feat: indie status page MVP -- FastAPI + SQLite

- 8 DB models (services, incidents, monitors, subscribers, etc.)
- Full CRUD API for services, incidents, monitors
- Public status page with live data
- Incident detail page with timeline
- API key authentication
- Uptime monitoring scheduler
- 13 tests passing
- TECHNICAL_DESIGN.md with full spec

venv/lib/python3.11/site-packages/mypy/__init__.py

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+# This page intentionally left blank

venv/lib/python3.11/site-packages/mypy/__main__.py

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+"""Mypy type checker command line tool."""
+
+from __future__ import annotations
+
+import os
+import sys
+import traceback
+
+from mypy.main import main, process_options
+from mypy.util import FancyFormatter
+
+
+def console_entry() -> None:
+    try:
+        main()
+        sys.stdout.flush()
+        sys.stderr.flush()
+    except BrokenPipeError:
+        # Python flushes standard streams on exit; redirect remaining output
+        # to devnull to avoid another BrokenPipeError at shutdown
+        devnull = os.open(os.devnull, os.O_WRONLY)
+        os.dup2(devnull, sys.stdout.fileno())
+        sys.exit(2)
+    except KeyboardInterrupt:
+        _, options = process_options(args=sys.argv[1:])
+        if options.show_traceback:
+            sys.stdout.write(traceback.format_exc())
+        formatter = FancyFormatter(sys.stdout, sys.stderr, False)
+        msg = "Interrupted\n"
+        sys.stdout.write(formatter.style(msg, color="red", bold=True))
+        sys.stdout.flush()
+        sys.stderr.flush()
+        sys.exit(2)
+    except Exception as e:
+        # Try reporting any uncaught error canonically, otherwise just flush the traceback.
+        try:
+            import mypy.errors
+
+            _, options = process_options(args=sys.argv[1:])
+            mypy.errors.report_internal_error(e, None, 0, None, options)
+        except Exception:
+            pass
+        sys.stdout.write(traceback.format_exc())
+        sys.stdout.flush()
+        sys.stderr.flush()
+        sys.exit(2)
+
+
+if __name__ == "__main__":
+    console_entry()

venv/lib/python3.11/site-packages/mypy/api.py

@@ -0,0 +1,95 @@
+"""This module makes it possible to use mypy as part of a Python application.
+
+Since mypy still changes, the API was kept utterly simple and non-intrusive.
+It just mimics command line activation without starting a new interpreter.
+So the normal docs about the mypy command line apply.
+Changes in the command line version of mypy will be immediately usable.
+
+Just import this module and then call the 'run' function with a parameter of
+type List[str], containing what normally would have been the command line
+arguments to mypy.
+
+Function 'run' returns a Tuple[str, str, int], namely
+(<normal_report>, <error_report>, <exit_status>),
+in which <normal_report> is what mypy normally writes to sys.stdout,
+<error_report> is what mypy normally writes to sys.stderr and exit_status is
+the exit status mypy normally returns to the operating system.
+
+Any pretty formatting is left to the caller.
+
+The 'run_dmypy' function is similar, but instead mimics invocation of
+dmypy. Note that run_dmypy is not thread-safe and modifies sys.stdout
+and sys.stderr during its invocation.
+
+Note that these APIs don't support incremental generation of error
+messages.
+
+Trivial example of code using this module:
+
+import sys
+from mypy import api
+
+result = api.run(sys.argv[1:])
+
+if result[0]:
+    print('\nType checking report:\n')
+    print(result[0])  # stdout
+
+if result[1]:
+    print('\nError report:\n')
+    print(result[1])  # stderr
+
+print('\nExit status:', result[2])
+
+"""
+
+from __future__ import annotations
+
+import sys
+from collections.abc import Callable
+from io import StringIO
+from typing import TextIO
+
+
+def _run(main_wrapper: Callable[[TextIO, TextIO], None]) -> tuple[str, str, int]:
+    stdout = StringIO()
+    stderr = StringIO()
+
+    try:
+        main_wrapper(stdout, stderr)
+        exit_status = 0
+    except SystemExit as system_exit:
+        assert isinstance(system_exit.code, int)
+        exit_status = system_exit.code
+
+    return stdout.getvalue(), stderr.getvalue(), exit_status
+
+
+def run(args: list[str]) -> tuple[str, str, int]:
+    # Lazy import to avoid needing to import all of mypy to call run_dmypy
+    from mypy.main import main
+
+    return _run(
+        lambda stdout, stderr: main(args=args, stdout=stdout, stderr=stderr, clean_exit=True)
+    )
+
+
+def run_dmypy(args: list[str]) -> tuple[str, str, int]:
+    from mypy.dmypy.client import main
+
+    # A bunch of effort has been put into threading stdout and stderr
+    # through the main API to avoid the threadsafety problems of
+    # modifying sys.stdout/sys.stderr, but that hasn't been done for
+    # the dmypy client, so we just do the non-threadsafe thing.
+    def f(stdout: TextIO, stderr: TextIO) -> None:
+        old_stdout = sys.stdout
+        old_stderr = sys.stderr
+        try:
+            sys.stdout = stdout
+            sys.stderr = stderr
+            main(args)
+        finally:
+            sys.stdout = old_stdout
+            sys.stderr = old_stderr
+
+    return _run(f)

venv/lib/python3.11/site-packages/mypy/applytype.py

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+from __future__ import annotations
+
+from collections.abc import Callable, Iterable, Sequence
+
+import mypy.subtypes
+from mypy.erasetype import erase_typevars
+from mypy.expandtype import expand_type
+from mypy.nodes import Context, TypeInfo
+from mypy.type_visitor import TypeTranslator
+from mypy.typeops import get_all_type_vars
+from mypy.types import (
+    AnyType,
+    CallableType,
+    Instance,
+    Parameters,
+    ParamSpecFlavor,
+    ParamSpecType,
+    PartialType,
+    ProperType,
+    Type,
+    TypeAliasType,
+    TypeVarId,
+    TypeVarLikeType,
+    TypeVarTupleType,
+    TypeVarType,
+    UninhabitedType,
+    UnpackType,
+    get_proper_type,
+    remove_dups,
+)
+
+
+def get_target_type(
+    tvar: TypeVarLikeType,
+    type: Type,
+    callable: CallableType,
+    report_incompatible_typevar_value: Callable[[CallableType, Type, str, Context], None],
+    context: Context,
+    skip_unsatisfied: bool,
+) -> Type | None:
+    p_type = get_proper_type(type)
+    if isinstance(p_type, UninhabitedType) and tvar.has_default():
+        return tvar.default
+    if isinstance(tvar, ParamSpecType):
+        return type
+    if isinstance(tvar, TypeVarTupleType):
+        return type
+    assert isinstance(tvar, TypeVarType)
+    values = tvar.values
+    if values:
+        if isinstance(p_type, AnyType):
+            return type
+        if isinstance(p_type, TypeVarType) and p_type.values:
+            # Allow substituting T1 for T if every allowed value of T1
+            # is also a legal value of T.
+            if all(any(mypy.subtypes.is_same_type(v, v1) for v in values) for v1 in p_type.values):
+                return type
+        matching = []
+        for value in values:
+            if mypy.subtypes.is_subtype(type, value):
+                matching.append(value)
+        if matching:
+            best = matching[0]
+            # If there are more than one matching value, we select the narrowest
+            for match in matching[1:]:
+                if mypy.subtypes.is_subtype(match, best):
+                    best = match
+            return best
+        if skip_unsatisfied:
+            return None
+        report_incompatible_typevar_value(callable, type, tvar.name, context)
+    else:
+        upper_bound = tvar.upper_bound
+        if tvar.name == "Self":
+            # Internally constructed Self-types contain class type variables in upper bound,
+            # so we need to erase them to avoid false positives. This is safe because we do
+            # not support type variables in upper bounds of user defined types.
+            upper_bound = erase_typevars(upper_bound)
+        if not mypy.subtypes.is_subtype(type, upper_bound):
+            if skip_unsatisfied:
+                return None
+            report_incompatible_typevar_value(callable, type, tvar.name, context)
+    return type
+
+
+def apply_generic_arguments(
+    callable: CallableType,
+    orig_types: Sequence[Type | None],
+    report_incompatible_typevar_value: Callable[[CallableType, Type, str, Context], None],
+    context: Context,
+    skip_unsatisfied: bool = False,
+) -> CallableType:
+    """Apply generic type arguments to a callable type.
+
+    For example, applying [int] to 'def [T] (T) -> T' results in
+    'def (int) -> int'.
+
+    Note that each type can be None; in this case, it will not be applied.
+
+    If `skip_unsatisfied` is True, then just skip the types that don't satisfy type variable
+    bound or constraints, instead of giving an error.
+    """
+    tvars = callable.variables
+    assert len(orig_types) <= len(tvars)
+    # Check that inferred type variable values are compatible with allowed
+    # values and bounds.  Also, promote subtype values to allowed values.
+    # Create a map from type variable id to target type.
+    id_to_type: dict[TypeVarId, Type] = {}
+
+    for tvar, type in zip(tvars, orig_types):
+        assert not isinstance(type, PartialType), "Internal error: must never apply partial type"
+        if type is None:
+            continue
+
+        target_type = get_target_type(
+            tvar, type, callable, report_incompatible_typevar_value, context, skip_unsatisfied
+        )
+        if target_type is not None:
+            id_to_type[tvar.id] = target_type
+
+    # TODO: validate arg_kinds/arg_names for ParamSpec and TypeVarTuple replacements,
+    # not just type variable bounds above.
+    param_spec = callable.param_spec()
+    if param_spec is not None:
+        nt = id_to_type.get(param_spec.id)
+        if nt is not None:
+            # ParamSpec expansion is special-cased, so we need to always expand callable
+            # as a whole, not expanding arguments individually.
+            callable = expand_type(callable, id_to_type)
+            assert isinstance(callable, CallableType)
+            return callable.copy_modified(
+                variables=[tv for tv in tvars if tv.id not in id_to_type]
+            )
+
+    # Apply arguments to argument types.
+    var_arg = callable.var_arg()
+    if var_arg is not None and isinstance(var_arg.typ, UnpackType):
+        # Same as for ParamSpec, callable with variadic types needs to be expanded as a whole.
+        callable = expand_type(callable, id_to_type)
+        assert isinstance(callable, CallableType)
+        return callable.copy_modified(variables=[tv for tv in tvars if tv.id not in id_to_type])
+    else:
+        callable = callable.copy_modified(
+            arg_types=[expand_type(at, id_to_type) for at in callable.arg_types]
+        )
+
+    # Apply arguments to TypeGuard and TypeIs if any.
+    if callable.type_guard is not None:
+        type_guard = expand_type(callable.type_guard, id_to_type)
+    else:
+        type_guard = None
+    if callable.type_is is not None:
+        type_is = expand_type(callable.type_is, id_to_type)
+    else:
+        type_is = None
+
+    # The callable may retain some type vars if only some were applied.
+    # TODO: move apply_poly() logic here when new inference
+    # becomes universally used (i.e. in all passes + in unification).
+    # With this new logic we can actually *add* some new free variables.
+    remaining_tvars: list[TypeVarLikeType] = []
+    for tv in tvars:
+        if tv.id in id_to_type:
+            continue
+        if not tv.has_default():
+            remaining_tvars.append(tv)
+            continue
+        # TypeVarLike isn't in id_to_type mapping.
+        # Only expand the TypeVar default here.
+        typ = expand_type(tv, id_to_type)
+        assert isinstance(typ, TypeVarLikeType)
+        remaining_tvars.append(typ)
+
+    return callable.copy_modified(
+        ret_type=expand_type(callable.ret_type, id_to_type),
+        variables=remaining_tvars,
+        type_guard=type_guard,
+        type_is=type_is,
+    )
+
+
+def apply_poly(tp: CallableType, poly_tvars: Sequence[TypeVarLikeType]) -> CallableType | None:
+    """Make free type variables generic in the type if possible.
+
+    This will translate the type `tp` while trying to create valid bindings for
+    type variables `poly_tvars` while traversing the type. This follows the same rules
+    as we do during semantic analysis phase, examples:
+      * Callable[Callable[[T], T], T] -> def [T] (def (T) -> T) -> T
+      * Callable[[], Callable[[T], T]] -> def () -> def [T] (T -> T)
+      * List[T] -> None (not possible)
+    """
+    try:
+        return tp.copy_modified(
+            arg_types=[t.accept(PolyTranslator(poly_tvars)) for t in tp.arg_types],
+            ret_type=tp.ret_type.accept(PolyTranslator(poly_tvars)),
+            variables=[],
+        )
+    except PolyTranslationError:
+        return None
+
+
+class PolyTranslationError(Exception):
+    pass
+
+
+class PolyTranslator(TypeTranslator):
+    """Make free type variables generic in the type if possible.
+
+    See docstring for apply_poly() for details.
+    """
+
+    def __init__(
+        self,
+        poly_tvars: Iterable[TypeVarLikeType],
+        bound_tvars: frozenset[TypeVarLikeType] = frozenset(),
+        seen_aliases: frozenset[TypeInfo] = frozenset(),
+    ) -> None:
+        super().__init__()
+        self.poly_tvars = set(poly_tvars)
+        # This is a simplified version of TypeVarScope used during semantic analysis.
+        self.bound_tvars = bound_tvars
+        self.seen_aliases = seen_aliases
+
+    def collect_vars(self, t: CallableType | Parameters) -> list[TypeVarLikeType]:
+        found_vars = []
+        for arg in t.arg_types:
+            for tv in get_all_type_vars(arg):
+                if isinstance(tv, ParamSpecType):
+                    normalized: TypeVarLikeType = tv.copy_modified(
+                        flavor=ParamSpecFlavor.BARE, prefix=Parameters([], [], [])
+                    )
+                else:
+                    normalized = tv
+                if normalized in self.poly_tvars and normalized not in self.bound_tvars:
+                    found_vars.append(normalized)
+        return remove_dups(found_vars)
+
+    def visit_callable_type(self, t: CallableType) -> Type:
+        found_vars = self.collect_vars(t)
+        self.bound_tvars |= set(found_vars)
+        result = super().visit_callable_type(t)
+        self.bound_tvars -= set(found_vars)
+
+        assert isinstance(result, ProperType) and isinstance(result, CallableType)
+        result.variables = result.variables + tuple(found_vars)
+        return result
+
+    def visit_type_var(self, t: TypeVarType) -> Type:
+        if t in self.poly_tvars and t not in self.bound_tvars:
+            raise PolyTranslationError()
+        return super().visit_type_var(t)
+
+    def visit_param_spec(self, t: ParamSpecType) -> Type:
+        if t in self.poly_tvars and t not in self.bound_tvars:
+            raise PolyTranslationError()
+        return super().visit_param_spec(t)
+
+    def visit_type_var_tuple(self, t: TypeVarTupleType) -> Type:
+        if t in self.poly_tvars and t not in self.bound_tvars:
+            raise PolyTranslationError()
+        return super().visit_type_var_tuple(t)
+
+    def visit_type_alias_type(self, t: TypeAliasType) -> Type:
+        if not t.args:
+            return t.copy_modified()
+        if not t.is_recursive:
+            return get_proper_type(t).accept(self)
+        # We can't handle polymorphic application for recursive generic aliases
+        # without risking an infinite recursion, just give up for now.
+        raise PolyTranslationError()
+
+    def visit_instance(self, t: Instance) -> Type:
+        if t.type.has_param_spec_type:
+            # We need this special-casing to preserve the possibility to store a
+            # generic function in an instance type. Things like
+            #     forall T . Foo[[x: T], T]
+            # are not really expressible in current type system, but this looks like
+            # a useful feature, so let's keep it.
+            param_spec_index = next(
+                i for (i, tv) in enumerate(t.type.defn.type_vars) if isinstance(tv, ParamSpecType)
+            )
+            p = get_proper_type(t.args[param_spec_index])
+            if isinstance(p, Parameters):
+                found_vars = self.collect_vars(p)
+                self.bound_tvars |= set(found_vars)
+                new_args = [a.accept(self) for a in t.args]
+                self.bound_tvars -= set(found_vars)
+
+                repl = new_args[param_spec_index]
+                assert isinstance(repl, ProperType) and isinstance(repl, Parameters)
+                repl.variables = list(repl.variables) + list(found_vars)
+                return t.copy_modified(args=new_args)
+        # There is the same problem with callback protocols as with aliases
+        # (callback protocols are essentially more flexible aliases to callables).
+        if t.args and t.type.is_protocol and t.type.protocol_members == ["__call__"]:
+            if t.type in self.seen_aliases:
+                raise PolyTranslationError()
+            call = mypy.subtypes.find_member("__call__", t, t, is_operator=True)
+            assert call is not None
+            return call.accept(
+                PolyTranslator(self.poly_tvars, self.bound_tvars, self.seen_aliases | {t.type})
+            )
+        return super().visit_instance(t)

venv/lib/python3.11/site-packages/mypy/argmap.py

@@ -0,0 +1,269 @@
+"""Utilities for mapping between actual and formal arguments (and their types)."""
+
+from __future__ import annotations
+
+from collections.abc import Callable, Sequence
+from typing import TYPE_CHECKING
+
+from mypy import nodes
+from mypy.maptype import map_instance_to_supertype
+from mypy.types import (
+    AnyType,
+    Instance,
+    ParamSpecType,
+    TupleType,
+    Type,
+    TypedDictType,
+    TypeOfAny,
+    TypeVarTupleType,
+    UnpackType,
+    get_proper_type,
+)
+
+if TYPE_CHECKING:
+    from mypy.infer import ArgumentInferContext
+
+
+def map_actuals_to_formals(
+    actual_kinds: list[nodes.ArgKind],
+    actual_names: Sequence[str | None] | None,
+    formal_kinds: list[nodes.ArgKind],
+    formal_names: Sequence[str | None],
+    actual_arg_type: Callable[[int], Type],
+) -> list[list[int]]:
+    """Calculate mapping between actual (caller) args and formals.
+
+    The result contains a list of caller argument indexes mapping to each
+    callee argument index, indexed by callee index.
+
+    The actual_arg_type argument should evaluate to the type of the actual
+    argument with the given index.
+    """
+    nformals = len(formal_kinds)
+    formal_to_actual: list[list[int]] = [[] for i in range(nformals)]
+    ambiguous_actual_kwargs: list[int] = []
+    fi = 0
+    for ai, actual_kind in enumerate(actual_kinds):
+        if actual_kind == nodes.ARG_POS:
+            if fi < nformals:
+                if not formal_kinds[fi].is_star():
+                    formal_to_actual[fi].append(ai)
+                    fi += 1
+                elif formal_kinds[fi] == nodes.ARG_STAR:
+                    formal_to_actual[fi].append(ai)
+        elif actual_kind == nodes.ARG_STAR:
+            # We need to know the actual type to map varargs.
+            actualt = get_proper_type(actual_arg_type(ai))
+            if isinstance(actualt, TupleType):
+                # A tuple actual maps to a fixed number of formals.
+                for _ in range(len(actualt.items)):
+                    if fi < nformals:
+                        if formal_kinds[fi] != nodes.ARG_STAR2:
+                            formal_to_actual[fi].append(ai)
+                        else:
+                            break
+                        if formal_kinds[fi] != nodes.ARG_STAR:
+                            fi += 1
+            else:
+                # Assume that it is an iterable (if it isn't, there will be
+                # an error later).
+                while fi < nformals:
+                    if formal_kinds[fi].is_named(star=True):
+                        break
+                    else:
+                        formal_to_actual[fi].append(ai)
+                    if formal_kinds[fi] == nodes.ARG_STAR:
+                        break
+                    fi += 1
+        elif actual_kind.is_named():
+            assert actual_names is not None, "Internal error: named kinds without names given"
+            name = actual_names[ai]
+            if name in formal_names and formal_kinds[formal_names.index(name)] != nodes.ARG_STAR:
+                formal_to_actual[formal_names.index(name)].append(ai)
+            elif nodes.ARG_STAR2 in formal_kinds:
+                formal_to_actual[formal_kinds.index(nodes.ARG_STAR2)].append(ai)
+        else:
+            assert actual_kind == nodes.ARG_STAR2
+            actualt = get_proper_type(actual_arg_type(ai))
+            if isinstance(actualt, TypedDictType):
+                for name in actualt.items:
+                    if name in formal_names:
+                        formal_to_actual[formal_names.index(name)].append(ai)
+                    elif nodes.ARG_STAR2 in formal_kinds:
+                        formal_to_actual[formal_kinds.index(nodes.ARG_STAR2)].append(ai)
+            else:
+                # We don't exactly know which **kwargs are provided by the
+                # caller, so we'll defer until all the other unambiguous
+                # actuals have been processed
+                ambiguous_actual_kwargs.append(ai)
+
+    if ambiguous_actual_kwargs:
+        # Assume the ambiguous kwargs will fill the remaining arguments.
+        #
+        # TODO: If there are also tuple varargs, we might be missing some potential
+        #       matches if the tuple was short enough to not match everything.
+        unmatched_formals = [
+            fi
+            for fi in range(nformals)
+            if (
+                formal_names[fi]
+                and (
+                    not formal_to_actual[fi]
+                    or actual_kinds[formal_to_actual[fi][0]] == nodes.ARG_STAR
+                )
+                and formal_kinds[fi] != nodes.ARG_STAR
+            )
+            or formal_kinds[fi] == nodes.ARG_STAR2
+        ]
+        for ai in ambiguous_actual_kwargs:
+            for fi in unmatched_formals:
+                formal_to_actual[fi].append(ai)
+
+    return formal_to_actual
+
+
+def map_formals_to_actuals(
+    actual_kinds: list[nodes.ArgKind],
+    actual_names: Sequence[str | None] | None,
+    formal_kinds: list[nodes.ArgKind],
+    formal_names: list[str | None],
+    actual_arg_type: Callable[[int], Type],
+) -> list[list[int]]:
+    """Calculate the reverse mapping of map_actuals_to_formals."""
+    formal_to_actual = map_actuals_to_formals(
+        actual_kinds, actual_names, formal_kinds, formal_names, actual_arg_type
+    )
+    # Now reverse the mapping.
+    actual_to_formal: list[list[int]] = [[] for _ in actual_kinds]
+    for formal, actuals in enumerate(formal_to_actual):
+        for actual in actuals:
+            actual_to_formal[actual].append(formal)
+    return actual_to_formal
+
+
+class ArgTypeExpander:
+    """Utility class for mapping actual argument types to formal arguments.
+
+    One of the main responsibilities is to expand caller tuple *args and TypedDict
+    **kwargs, and to keep track of which tuple/TypedDict items have already been
+    consumed.
+
+    Example:
+
+       def f(x: int, *args: str) -> None: ...
+       f(*(1, 'x', 1.1))
+
+    We'd call expand_actual_type three times:
+
+      1. The first call would provide 'int' as the actual type of 'x' (from '1').
+      2. The second call would provide 'str' as one of the actual types for '*args'.
+      2. The third call would provide 'float' as one of the actual types for '*args'.
+
+    A single instance can process all the arguments for a single call. Each call
+    needs a separate instance since instances have per-call state.
+    """
+
+    def __init__(self, context: ArgumentInferContext) -> None:
+        # Next tuple *args index to use.
+        self.tuple_index = 0
+        # Keyword arguments in TypedDict **kwargs used.
+        self.kwargs_used: set[str] | None = None
+        # Type context for `*` and `**` arg kinds.
+        self.context = context
+
+    def expand_actual_type(
+        self,
+        actual_type: Type,
+        actual_kind: nodes.ArgKind,
+        formal_name: str | None,
+        formal_kind: nodes.ArgKind,
+        allow_unpack: bool = False,
+    ) -> Type:
+        """Return the actual (caller) type(s) of a formal argument with the given kinds.
+
+        If the actual argument is a tuple *args, return the next individual tuple item that
+        maps to the formal arg.
+
+        If the actual argument is a TypedDict **kwargs, return the next matching typed dict
+        value type based on formal argument name and kind.
+
+        This is supposed to be called for each formal, in order. Call multiple times per
+        formal if multiple actuals map to a formal.
+        """
+        original_actual = actual_type
+        actual_type = get_proper_type(actual_type)
+        if actual_kind == nodes.ARG_STAR:
+            if isinstance(actual_type, TypeVarTupleType):
+                # This code path is hit when *Ts is passed to a callable and various
+                # special-handling didn't catch this. The best thing we can do is to use
+                # the upper bound.
+                actual_type = get_proper_type(actual_type.upper_bound)
+            if isinstance(actual_type, Instance) and actual_type.args:
+                from mypy.subtypes import is_subtype
+
+                if is_subtype(actual_type, self.context.iterable_type):
+                    return map_instance_to_supertype(
+                        actual_type, self.context.iterable_type.type
+                    ).args[0]
+                else:
+                    # We cannot properly unpack anything other
+                    # than `Iterable` type with `*`.
+                    # Just return `Any`, other parts of code would raise
+                    # a different error for improper use.
+                    return AnyType(TypeOfAny.from_error)
+            elif isinstance(actual_type, TupleType):
+                # Get the next tuple item of a tuple *arg.
+                if self.tuple_index >= len(actual_type.items):
+                    # Exhausted a tuple -- continue to the next *args.
+                    self.tuple_index = 1
+                else:
+                    self.tuple_index += 1
+                item = actual_type.items[self.tuple_index - 1]
+                if isinstance(item, UnpackType) and not allow_unpack:
+                    # An unpack item that doesn't have special handling, use upper bound as above.
+                    unpacked = get_proper_type(item.type)
+                    if isinstance(unpacked, TypeVarTupleType):
+                        fallback = get_proper_type(unpacked.upper_bound)
+                    else:
+                        fallback = unpacked
+                    assert (
+                        isinstance(fallback, Instance)
+                        and fallback.type.fullname == "builtins.tuple"
+                    )
+                    item = fallback.args[0]
+                return item
+            elif isinstance(actual_type, ParamSpecType):
+                # ParamSpec is valid in *args but it can't be unpacked.
+                return actual_type
+            else:
+                return AnyType(TypeOfAny.from_error)
+        elif actual_kind == nodes.ARG_STAR2:
+            from mypy.subtypes import is_subtype
+
+            if isinstance(actual_type, TypedDictType):
+                if self.kwargs_used is None:
+                    self.kwargs_used = set()
+                if formal_kind != nodes.ARG_STAR2 and formal_name in actual_type.items:
+                    # Lookup type based on keyword argument name.
+                    assert formal_name is not None
+                else:
+                    # Pick an arbitrary item if no specified keyword is expected.
+                    formal_name = (set(actual_type.items.keys()) - self.kwargs_used).pop()
+                self.kwargs_used.add(formal_name)
+                return actual_type.items[formal_name]
+            elif isinstance(actual_type, Instance) and is_subtype(
+                actual_type, self.context.mapping_type
+            ):
+                # Only `Mapping` type can be unpacked with `**`.
+                # Other types will produce an error somewhere else.
+                return map_instance_to_supertype(actual_type, self.context.mapping_type.type).args[
+                    1
+                ]
+            elif isinstance(actual_type, ParamSpecType):
+                # ParamSpec is valid in **kwargs but it can't be unpacked.
+                return actual_type
+            else:
+                return AnyType(TypeOfAny.from_error)
+        else:
+            # No translation for other kinds -- 1:1 mapping.
+            return original_actual

venv/lib/python3.11/site-packages/mypy/binder.py

@@ -0,0 +1,709 @@
+from __future__ import annotations
+
+from collections import defaultdict
+from collections.abc import Iterator
+from contextlib import contextmanager
+from typing import Literal, NamedTuple, TypeAlias as _TypeAlias
+
+from mypy.erasetype import remove_instance_last_known_values
+from mypy.literals import Key, extract_var_from_literal_hash, literal, literal_hash, subkeys
+from mypy.nodes import (
+    LITERAL_NO,
+    Expression,
+    IndexExpr,
+    MemberExpr,
+    NameExpr,
+    RefExpr,
+    TypeInfo,
+    Var,
+)
+from mypy.options import Options
+from mypy.subtypes import is_same_type, is_subtype
+from mypy.typeops import make_simplified_union
+from mypy.types import (
+    AnyType,
+    Instance,
+    NoneType,
+    PartialType,
+    ProperType,
+    TupleType,
+    Type,
+    TypeOfAny,
+    TypeType,
+    TypeVarType,
+    UnionType,
+    UnpackType,
+    find_unpack_in_list,
+    flatten_nested_unions,
+    get_proper_type,
+)
+from mypy.typevars import fill_typevars_with_any
+
+BindableExpression: _TypeAlias = IndexExpr | MemberExpr | NameExpr
+
+
+class CurrentType(NamedTuple):
+    type: Type
+    from_assignment: bool
+
+
+class Frame:
+    """A Frame represents a specific point in the execution of a program.
+
+    It carries information about the current types of expressions at
+    that point, arising either from assignments to those expressions
+    or the result of isinstance checks and other type narrowing
+    operations. It also records whether it is possible to reach that
+    point at all.
+
+    We add a new frame wherenever there is a new scope or control flow
+    branching.
+
+    This information is not copied into a new Frame when it is pushed
+    onto the stack, so a given Frame only has information about types
+    that were assigned in that frame.
+
+    Expressions are stored in dicts using 'literal hashes' as keys (type
+    "Key"). These are hashable values derived from expression AST nodes
+    (only those that can be narrowed). literal_hash(expr) is used to
+    calculate the hashes. Note that this isn't directly related to literal
+    types -- the concept predates literal types.
+    """
+
+    def __init__(self, id: int, conditional_frame: bool = False) -> None:
+        self.id = id
+        self.types: dict[Key, CurrentType] = {}
+        self.unreachable = False
+        self.conditional_frame = conditional_frame
+        self.suppress_unreachable_warnings = False
+
+    def __repr__(self) -> str:
+        return f"Frame({self.id}, {self.types}, {self.unreachable}, {self.conditional_frame})"
+
+
+Assigns = defaultdict[Expression, list[tuple[Type, Type | None]]]
+
+
+class FrameContext:
+    """Context manager pushing a Frame to ConditionalTypeBinder.
+
+    See frame_context() below for documentation on parameters. We use this class
+    instead of @contextmanager as a mypyc-specific performance optimization.
+    """
+
+    def __init__(
+        self,
+        binder: ConditionalTypeBinder,
+        can_skip: bool,
+        fall_through: int,
+        break_frame: int,
+        continue_frame: int,
+        conditional_frame: bool,
+        try_frame: bool,
+        discard: bool,
+    ) -> None:
+        self.binder = binder
+        self.can_skip = can_skip
+        self.fall_through = fall_through
+        self.break_frame = break_frame
+        self.continue_frame = continue_frame
+        self.conditional_frame = conditional_frame
+        self.try_frame = try_frame
+        self.discard = discard
+
+    def __enter__(self) -> Frame:
+        assert len(self.binder.frames) > 1
+
+        if self.break_frame:
+            self.binder.break_frames.append(len(self.binder.frames) - self.break_frame)
+        if self.continue_frame:
+            self.binder.continue_frames.append(len(self.binder.frames) - self.continue_frame)
+        if self.try_frame:
+            self.binder.try_frames.add(len(self.binder.frames) - 1)
+
+        new_frame = self.binder.push_frame(self.conditional_frame)
+        if self.try_frame:
+            # An exception may occur immediately
+            self.binder.allow_jump(-1)
+        return new_frame
+
+    def __exit__(self, exc_type: object, exc_val: object, exc_tb: object) -> Literal[False]:
+        self.binder.pop_frame(self.can_skip, self.fall_through, discard=self.discard)
+
+        if self.break_frame:
+            self.binder.break_frames.pop()
+        if self.continue_frame:
+            self.binder.continue_frames.pop()
+        if self.try_frame:
+            self.binder.try_frames.remove(len(self.binder.frames) - 1)
+        return False
+
+
+class ConditionalTypeBinder:
+    """Keep track of conditional types of variables.
+
+    NB: Variables are tracked by literal hashes of expressions, so it is
+    possible to confuse the binder when there is aliasing. Example:
+
+        class A:
+            a: int | str
+
+        x = A()
+        lst = [x]
+        reveal_type(x.a)      # int | str
+        x.a = 1
+        reveal_type(x.a)      # int
+        reveal_type(lst[0].a) # int | str
+        lst[0].a = 'a'
+        reveal_type(x.a)      # int
+        reveal_type(lst[0].a) # str
+    """
+
+    # Stored assignments for situations with tuple/list lvalue and rvalue of union type.
+    # This maps an expression to a list of bound types for every item in the union type.
+    type_assignments: Assigns | None = None
+
+    def __init__(self, options: Options) -> None:
+        # Each frame gets an increasing, distinct id.
+        self.next_id = 1
+
+        # The stack of frames currently used.  These map
+        # literal_hash(expr) -- literals like 'foo.bar' --
+        # to types. The last element of this list is the
+        # top-most, current frame. Each earlier element
+        # records the state as of when that frame was last
+        # on top of the stack.
+        self.frames = [Frame(self._get_id())]
+
+        # For frames higher in the stack, we record the set of
+        # Frames that can escape there, either by falling off
+        # the end of the frame or by a loop control construct
+        # or raised exception. The last element of self.frames
+        # has no corresponding element in this list.
+        self.options_on_return: list[list[Frame]] = []
+
+        # Maps literal_hash(expr) to get_declaration(expr)
+        # for every expr stored in the binder
+        self.declarations: dict[Key, Type | None] = {}
+        # Set of other keys to invalidate if a key is changed, e.g. x -> {x.a, x[0]}
+        # Whenever a new key (e.g. x.a.b) is added, we update this
+        self.dependencies: dict[Key, set[Key]] = {}
+
+        # Whether the last pop changed the newly top frame on exit
+        self.last_pop_changed = False
+
+        # These are used to track control flow in try statements and loops.
+        self.try_frames: set[int] = set()
+        self.break_frames: list[int] = []
+        self.continue_frames: list[int] = []
+
+        # If True, initial assignment to a simple variable (e.g. "x", but not "x.y")
+        # is added to the binder. This allows more precise narrowing and more
+        # flexible inference of variable types (--allow-redefinition-new).
+        self.bind_all = options.allow_redefinition_new
+
+        # This tracks any externally visible changes in binder to invalidate
+        # expression caches when needed.
+        self.version = 0
+
+    def _get_id(self) -> int:
+        self.next_id += 1
+        return self.next_id
+
+    def _add_dependencies(self, key: Key, value: Key | None = None) -> None:
+        if value is None:
+            value = key
+        else:
+            self.dependencies.setdefault(key, set()).add(value)
+        for elt in subkeys(key):
+            self._add_dependencies(elt, value)
+
+    def push_frame(self, conditional_frame: bool = False) -> Frame:
+        """Push a new frame into the binder."""
+        f = Frame(self._get_id(), conditional_frame)
+        self.frames.append(f)
+        self.options_on_return.append([])
+        return f
+
+    def _put(self, key: Key, type: Type, from_assignment: bool, index: int = -1) -> None:
+        self.version += 1
+        self.frames[index].types[key] = CurrentType(type, from_assignment)
+
+    def _get(self, key: Key, index: int = -1) -> CurrentType | None:
+        if index < 0:
+            index += len(self.frames)
+        for i in range(index, -1, -1):
+            if key in self.frames[i].types:
+                return self.frames[i].types[key]
+        return None
+
+    @classmethod
+    def can_put_directly(cls, expr: Expression) -> bool:
+        """Will `.put()` on this expression be successful?
+
+        This is inlined in `.put()` because the logic is rather hot and must be kept
+        in sync.
+        """
+        return isinstance(expr, (IndexExpr, MemberExpr, NameExpr)) and literal(expr) > LITERAL_NO
+
+    def put(self, expr: Expression, typ: Type, *, from_assignment: bool = True) -> None:
+        """Directly set the narrowed type of expression (if it supports it).
+
+        This is used for isinstance() etc. Assignments should go through assign_type().
+        """
+        if not isinstance(expr, (IndexExpr, MemberExpr, NameExpr)):
+            return
+        if not literal(expr):
+            return
+        key = literal_hash(expr)
+        assert key is not None, "Internal error: binder tried to put non-literal"
+        if key not in self.declarations:
+            self.declarations[key] = get_declaration(expr)
+            self._add_dependencies(key)
+        self._put(key, typ, from_assignment)
+
+    def unreachable(self) -> None:
+        self.version += 1
+        self.frames[-1].unreachable = True
+
+    def suppress_unreachable_warnings(self) -> None:
+        self.frames[-1].suppress_unreachable_warnings = True
+
+    def get(self, expr: Expression) -> Type | None:
+        key = literal_hash(expr)
+        assert key is not None, "Internal error: binder tried to get non-literal"
+        found = self._get(key)
+        if found is None:
+            return None
+        return found.type
+
+    def is_unreachable(self) -> bool:
+        # TODO: Copy the value of unreachable into new frames to avoid
+        # this traversal on every statement?
+        return any(f.unreachable for f in self.frames)
+
+    def is_unreachable_warning_suppressed(self) -> bool:
+        return any(f.suppress_unreachable_warnings for f in self.frames)
+
+    def cleanse(self, expr: Expression) -> None:
+        """Remove all references to a Node from the binder."""
+        key = literal_hash(expr)
+        assert key is not None, "Internal error: binder tried cleanse non-literal"
+        self._cleanse_key(key)
+
+    def _cleanse_key(self, key: Key) -> None:
+        """Remove all references to a key from the binder."""
+        for frame in self.frames:
+            if key in frame.types:
+                del frame.types[key]
+
+    def update_from_options(self, frames: list[Frame]) -> bool:
+        """Update the frame to reflect that each key will be updated
+        as in one of the frames.  Return whether any item changes.
+
+        If a key is declared as AnyType, only update it if all the
+        options are the same.
+        """
+        all_reachable = all(not f.unreachable for f in frames)
+        if not all_reachable:
+            frames = [f for f in frames if not f.unreachable]
+        changed = False
+        keys = [key for f in frames for key in f.types]
+        if len(keys) > 1:
+            keys = list(set(keys))
+        for key in keys:
+            current_value = self._get(key)
+            resulting_values = [f.types.get(key, current_value) for f in frames]
+            # Keys can be narrowed using two different semantics. The new semantics
+            # is enabled for inferred variables when bind_all is true, and it allows
+            # variable types to be widened using subsequent assignments. This is
+            # not allowed for instance attributes and annotated variables.
+            var = extract_var_from_literal_hash(key)
+            old_semantics = (
+                not self.bind_all or var is None or not var.is_inferred and not var.is_argument
+            )
+            if old_semantics and any(x is None for x in resulting_values):
+                # We didn't know anything about key before
+                # (current_value must be None), and we still don't
+                # know anything about key in at least one possible frame.
+                continue
+
+            resulting_values = [x for x in resulting_values if x is not None]
+
+            if all_reachable and all(not x.from_assignment for x in resulting_values):
+                # Do not synthesize a new type if we encountered a conditional block
+                # (if, while or match-case) without assignments.
+                # See check-isinstance.test::testNoneCheckDoesNotMakeTypeVarOptional
+                # This is a safe assumption: the fact that we checked something with `is`
+                # or `isinstance` does not change the type of the value.
+                continue
+
+            # Remove exact duplicates to save pointless work later, this is
+            # a micro-optimization for --allow-redefinition-new.
+            seen_types = set()
+            resulting_types = []
+            for rv in resulting_values:
+                assert rv is not None
+                if rv.type in seen_types:
+                    continue
+                resulting_types.append(rv.type)
+                seen_types.add(rv.type)
+
+            type = resulting_types[0]
+            declaration_type = get_proper_type(self.declarations.get(key))
+            if isinstance(declaration_type, AnyType):
+                # At this point resulting values can't contain None, see continue above
+                if not all(is_same_type(type, t) for t in resulting_types[1:]):
+                    type = AnyType(TypeOfAny.from_another_any, source_any=declaration_type)
+            else:
+                possible_types = []
+                for t in resulting_types:
+                    assert t is not None
+                    possible_types.append(t)
+                if len(possible_types) == 1:
+                    # This is to avoid calling get_proper_type() unless needed, as this may
+                    # interfere with our (hacky) TypeGuard support.
+                    type = possible_types[0]
+                else:
+                    type = make_simplified_union(possible_types)
+                    # Legacy guard for corner case when the original type is TypeVarType.
+                    if isinstance(declaration_type, TypeVarType) and not is_subtype(
+                        type, declaration_type
+                    ):
+                        type = declaration_type
+                    # Try simplifying resulting type for unions involving variadic tuples.
+                    # Technically, everything is still valid without this step, but if we do
+                    # not do this, this may create long unions after exiting an if check like:
+                    #     x: tuple[int, ...]
+                    #     if len(x) < 10:
+                    #         ...
+                    # We want the type of x to be tuple[int, ...] after this block (if it is
+                    # still equivalent to such type).
+                    if isinstance(type, UnionType):
+                        type = collapse_variadic_union(type)
+                    if (
+                        old_semantics
+                        and isinstance(type, ProperType)
+                        and isinstance(type, UnionType)
+                    ):
+                        # Simplify away any extra Any's that were added to the declared
+                        # type when popping a frame.
+                        simplified = UnionType.make_union(
+                            [t for t in type.items if not isinstance(get_proper_type(t), AnyType)]
+                        )
+                        if simplified == self.declarations[key]:
+                            type = simplified
+            if (
+                current_value is None
+                or not is_same_type(type, current_value.type)
+                # Manually carry over any narrowing from hasattr() from inner frames. This is
+                # a bit ad-hoc, but our handling of hasattr() is on best effort basis anyway.
+                or isinstance(p_type := get_proper_type(type), Instance)
+                and p_type.extra_attrs
+            ):
+                self._put(key, type, from_assignment=True)
+                if current_value is not None or extract_var_from_literal_hash(key) is None:
+                    # We definitely learned something new
+                    changed = True
+                elif not changed:
+                    # If there is no current value compare with the declaration. This prevents
+                    # reporting false changes in cases like this:
+                    #     x: int
+                    #     if foo():
+                    #         x = 1
+                    #     else:
+                    #         x = 2
+                    # We check partial types and widening in accept_loop() separately, so
+                    # this should be safe.
+                    changed = declaration_type is not None and not is_same_type(
+                        type, declaration_type
+                    )
+
+        self.frames[-1].unreachable = not frames
+
+        return changed
+
+    def pop_frame(self, can_skip: bool, fall_through: int, *, discard: bool = False) -> Frame:
+        """Pop a frame and return it.
+
+        See frame_context() for documentation of fall_through and discard.
+        """
+
+        if fall_through > 0:
+            self.allow_jump(-fall_through)
+
+        result = self.frames.pop()
+        options = self.options_on_return.pop()
+
+        if discard:
+            self.last_pop_changed = False
+            return result
+
+        if can_skip:
+            options.insert(0, self.frames[-1])
+
+        self.last_pop_changed = self.update_from_options(options)
+
+        return result
+
+    @contextmanager
+    def accumulate_type_assignments(self) -> Iterator[Assigns]:
+        """Push a new map to collect assigned types in multiassign from union.
+
+        If this map is not None, actual binding is deferred until all items in
+        the union are processed (a union of collected items is later bound
+        manually by the caller).
+        """
+        old_assignments = None
+        if self.type_assignments is not None:
+            old_assignments = self.type_assignments
+        self.type_assignments = defaultdict(list)
+        yield self.type_assignments
+        self.type_assignments = old_assignments
+
+    def assign_type(self, expr: Expression, type: Type, declared_type: Type | None) -> None:
+        """Narrow type of expression through an assignment.
+
+        Do nothing if the expression doesn't support narrowing.
+
+        When not narrowing though an assignment (isinstance() etc.), use put()
+        directly. This omits some special-casing logic for assignments.
+        """
+        # We should erase last known value in binder, because if we are using it,
+        # it means that the target is not final, and therefore can't hold a literal.
+        type = remove_instance_last_known_values(type)
+
+        if self.type_assignments is not None:
+            # We are in a multiassign from union, defer the actual binding,
+            # just collect the types.
+            self.type_assignments[expr].append((type, declared_type))
+            return
+        if not isinstance(expr, (IndexExpr, MemberExpr, NameExpr)):
+            return
+        if not literal(expr):
+            return
+        self.invalidate_dependencies(expr)
+
+        if declared_type is None:
+            # Not sure why this happens.  It seems to mainly happen in
+            # member initialization.
+            return
+        if not is_subtype(type, declared_type):
+            # Pretty sure this is only happens when there's a type error.
+
+            # Ideally this function wouldn't be called if the
+            # expression has a type error, though -- do other kinds of
+            # errors cause this function to get called at invalid
+            # times?
+            return
+
+        p_declared = get_proper_type(declared_type)
+        p_type = get_proper_type(type)
+        if isinstance(p_type, AnyType):
+            # Any type requires some special casing, for both historical reasons,
+            # and to optimise user experience without sacrificing correctness too much.
+            if isinstance(expr, RefExpr) and isinstance(expr.node, Var) and expr.node.is_inferred:
+                # First case: a local/global variable without explicit annotation,
+                # in this case we just assign Any (essentially following the SSA logic).
+                self.put(expr, type)
+            elif isinstance(p_declared, UnionType):
+                all_items = flatten_nested_unions(p_declared.items)
+                if any(isinstance(get_proper_type(item), NoneType) for item in all_items):
+                    # Second case: explicit optional type, in this case we optimize for
+                    # a common pattern when an untyped value used as a fallback replacing None.
+                    new_items = [
+                        type if isinstance(get_proper_type(item), NoneType) else item
+                        for item in all_items
+                    ]
+                    self.put(expr, UnionType(new_items))
+                elif any(isinstance(get_proper_type(item), AnyType) for item in all_items):
+                    # Third case: a union already containing Any (most likely from
+                    # an un-imported name), in this case we allow assigning Any as well.
+                    self.put(expr, type)
+                else:
+                    # In all other cases we don't narrow to Any to minimize false negatives.
+                    self.put(expr, declared_type)
+            else:
+                self.put(expr, declared_type)
+        elif isinstance(p_declared, AnyType):
+            # Mirroring the first case above, we don't narrow to a precise type if the variable
+            # has an explicit `Any` type annotation.
+            if isinstance(expr, RefExpr) and isinstance(expr.node, Var) and expr.node.is_inferred:
+                self.put(expr, type)
+            else:
+                self.put(expr, declared_type)
+        else:
+            self.put(expr, type)
+
+        for i in self.try_frames:
+            # XXX This should probably not copy the entire frame, but
+            # just copy this variable into a single stored frame.
+            self.allow_jump(i)
+
+    def invalidate_dependencies(self, expr: BindableExpression) -> None:
+        """Invalidate knowledge of types that include expr, but not expr itself.
+
+        For example, when expr is foo.bar, invalidate foo.bar.baz.
+
+        It is overly conservative: it invalidates globally, including
+        in code paths unreachable from here.
+        """
+        key = literal_hash(expr)
+        assert key is not None
+        for dep in self.dependencies.get(key, set()):
+            self._cleanse_key(dep)
+
+    def allow_jump(self, index: int) -> None:
+        # self.frames and self.options_on_return have different lengths
+        # so make sure the index is positive
+        if index < 0:
+            index += len(self.options_on_return)
+        frame = Frame(self._get_id())
+        for f in self.frames[index + 1 :]:
+            frame.types.update(f.types)
+            if f.unreachable:
+                frame.unreachable = True
+        self.options_on_return[index].append(frame)
+
+    def handle_break(self) -> None:
+        self.allow_jump(self.break_frames[-1])
+        self.unreachable()
+
+    def handle_continue(self) -> None:
+        self.allow_jump(self.continue_frames[-1])
+        self.unreachable()
+
+    def frame_context(
+        self,
+        *,
+        can_skip: bool,
+        fall_through: int = 1,
+        break_frame: int = 0,
+        continue_frame: int = 0,
+        conditional_frame: bool = False,
+        try_frame: bool = False,
+        discard: bool = False,
+    ) -> FrameContext:
+        """Return a context manager that pushes/pops frames on enter/exit.
+
+        If can_skip is True, control flow is allowed to bypass the
+        newly-created frame.
+
+        If fall_through > 0, then it will allow control flow that
+        falls off the end of the frame to escape to its ancestor
+        `fall_through` levels higher. Otherwise, control flow ends
+        at the end of the frame.
+
+        If break_frame > 0, then 'break' statements within this frame
+        will jump out to the frame break_frame levels higher than the
+        frame created by this call to frame_context. Similarly, for
+        continue_frame and 'continue' statements.
+
+        If try_frame is true, then execution is allowed to jump at any
+        point within the newly created frame (or its descendants) to
+        its parent (i.e., to the frame that was on top before this
+        call to frame_context).
+
+        If discard is True, then this is a temporary throw-away frame
+        (used e.g. for isolation) and its effect will be discarded on pop.
+
+        After the context manager exits, self.last_pop_changed indicates
+        whether any types changed in the newly-topmost frame as a result
+        of popping this frame.
+        """
+        return FrameContext(
+            self,
+            can_skip=can_skip,
+            fall_through=fall_through,
+            break_frame=break_frame,
+            continue_frame=continue_frame,
+            conditional_frame=conditional_frame,
+            try_frame=try_frame,
+            discard=discard,
+        )
+
+    @contextmanager
+    def top_frame_context(self) -> Iterator[Frame]:
+        """A variant of frame_context for use at the top level of
+        a namespace (module, function, or class).
+        """
+        assert len(self.frames) == 1
+        yield self.push_frame()
+        self.pop_frame(True, 0)
+        assert len(self.frames) == 1
+
+
+def get_declaration(expr: BindableExpression) -> Type | None:
+    """Get the declared or inferred type of a RefExpr expression.
+
+    Return None if there is no type or the expression is not a RefExpr.
+    This can return None if the type hasn't been inferred yet.
+    """
+    if isinstance(expr, RefExpr):
+        if isinstance(expr.node, Var):
+            type = expr.node.type
+            if not isinstance(get_proper_type(type), PartialType):
+                return type
+        elif isinstance(expr.node, TypeInfo):
+            return TypeType(fill_typevars_with_any(expr.node))
+    return None
+
+
+def collapse_variadic_union(typ: UnionType) -> Type:
+    """Simplify a union involving variadic tuple if possible.
+
+    This will collapse a type like e.g.
+        tuple[X, Z] | tuple[X, Y, Z] | tuple[X, Y, Y, *tuple[Y, ...], Z]
+    back to
+        tuple[X, *tuple[Y, ...], Z]
+    which is equivalent, but much simpler form of the same type.
+    """
+    tuple_items = []
+    other_items = []
+    for t in typ.items:
+        p_t = get_proper_type(t)
+        if isinstance(p_t, TupleType):
+            tuple_items.append(p_t)
+        else:
+            other_items.append(t)
+    if len(tuple_items) <= 1:
+        # This type cannot be simplified further.
+        return typ
+    tuple_items = sorted(tuple_items, key=lambda t: len(t.items))
+    first = tuple_items[0]
+    last = tuple_items[-1]
+    unpack_index = find_unpack_in_list(last.items)
+    if unpack_index is None:
+        return typ
+    unpack = last.items[unpack_index]
+    assert isinstance(unpack, UnpackType)
+    unpacked = get_proper_type(unpack.type)
+    if not isinstance(unpacked, Instance):
+        return typ
+    assert unpacked.type.fullname == "builtins.tuple"
+    suffix = last.items[unpack_index + 1 :]
+
+    # Check that first item matches the expected pattern and infer prefix.
+    if len(first.items) < len(suffix):
+        return typ
+    if suffix and first.items[-len(suffix) :] != suffix:
+        return typ
+    if suffix:
+        prefix = first.items[: -len(suffix)]
+    else:
+        prefix = first.items
+
+    # Check that all middle types match the expected pattern as well.
+    arg = unpacked.args[0]
+    for i, it in enumerate(tuple_items[1:-1]):
+        if it.items != prefix + [arg] * (i + 1) + suffix:
+            return typ
+
+    # Check the last item (the one with unpack), and choose an appropriate simplified type.
+    if last.items != prefix + [arg] * (len(typ.items) - 1) + [unpack] + suffix:
+        return typ
+    if len(first.items) == 0:
+        simplified: Type = unpacked.copy_modified()
+    else:
+        simplified = TupleType(prefix + [unpack] + suffix, fallback=last.partial_fallback)
+    return UnionType.make_union([simplified] + other_items)

venv/lib/python3.11/site-packages/mypy/bogus_type.py

@@ -0,0 +1,27 @@
+"""A Bogus[T] type alias for marking when we subvert the type system
+
+We need this for compiling with mypyc, which inserts runtime
+typechecks that cause problems when we subvert the type system. So
+when compiling with mypyc, we turn those places into Any, while
+keeping the types around for normal typechecks.
+
+Since this causes the runtime types to be Any, this is best used
+in places where efficient access to properties is not important.
+For those cases some other technique should be used.
+"""
+
+from __future__ import annotations
+
+from typing import Any, TypeVar
+
+from mypy_extensions import FlexibleAlias
+
+T = TypeVar("T")
+
+# This won't ever be true at runtime, but we consider it true during
+# mypyc compilations.
+MYPYC = False
+if MYPYC:
+    Bogus = FlexibleAlias[T, Any]
+else:
+    Bogus = FlexibleAlias[T, T]

venv/lib/python3.11/site-packages/mypy/build_worker/__main__.py

@@ -0,0 +1,6 @@
+from __future__ import annotations
+
+from mypy.build_worker.worker import console_entry
+
+if __name__ == "__main__":
+    console_entry()

venv/lib/python3.11/site-packages/mypy/build_worker/worker.py

@@ -0,0 +1,249 @@
+"""
+Mypy parallel build worker.
+
+The protocol of communication with the coordinator is as following:
+* Read (pickled) build options from command line.
+* Populate status file with pid and socket address.
+* Receive build sources from coordinator.
+* Load graph using the sources, and send ack to coordinator.
+* Receive SCC structure from coordinator, and ack it.
+* Receive an SCC id from coordinator, process it, and send back the results.
+* When prompted by coordinator (with a scc_id=None message), cleanup and shutdown.
+"""
+
+from __future__ import annotations
+
+import argparse
+import gc
+import json
+import os
+import pickle
+import platform
+import sys
+import time
+from typing import NamedTuple
+
+from librt.base64 import b64decode
+
+from mypy import util
+from mypy.build import (
+    SCC,
+    AckMessage,
+    BuildManager,
+    Graph,
+    GraphMessage,
+    SccRequestMessage,
+    SccResponseMessage,
+    SccsDataMessage,
+    SourcesDataMessage,
+    load_plugins,
+    process_stale_scc,
+)
+from mypy.defaults import RECURSION_LIMIT, WORKER_CONNECTION_TIMEOUT
+from mypy.errors import CompileError, ErrorInfo, Errors, report_internal_error
+from mypy.fscache import FileSystemCache
+from mypy.ipc import IPCException, IPCServer, receive, send
+from mypy.modulefinder import BuildSource, BuildSourceSet, compute_search_paths
+from mypy.nodes import FileRawData
+from mypy.options import Options
+from mypy.util import read_py_file
+from mypy.version import __version__
+
+parser = argparse.ArgumentParser(prog="mypy_worker", description="Mypy build worker")
+parser.add_argument("--status-file", help="status file to communicate worker details")
+parser.add_argument("--options-data", help="serialized mypy options")
+
+CONNECTION_NAME = "build_worker"
+
+
+class ServerContext(NamedTuple):
+    options: Options
+    disable_error_code: list[str]
+    enable_error_code: list[str]
+    errors: Errors
+    fscache: FileSystemCache
+
+
+def main(argv: list[str]) -> None:
+    # Set recursion limit and GC thresholds consistent with mypy/main.py
+    sys.setrecursionlimit(RECURSION_LIMIT)
+    if platform.python_implementation() == "CPython":
+        gc.set_threshold(200 * 1000, 30, 30)
+
+    args = parser.parse_args(argv)
+
+    # This mimics how daemon receives the options. Note we need to postpone
+    # processing error codes after plugins are loaded, because plugins can add
+    # custom error codes.
+    options_dict = pickle.loads(b64decode(args.options_data))
+    options_obj = Options()
+    disable_error_code = options_dict.pop("disable_error_code", [])
+    enable_error_code = options_dict.pop("enable_error_code", [])
+    options = options_obj.apply_changes(options_dict)
+
+    status_file = args.status_file
+    server = IPCServer(CONNECTION_NAME, WORKER_CONNECTION_TIMEOUT)
+
+    try:
+        with open(status_file, "w") as f:
+            json.dump({"pid": os.getpid(), "connection_name": server.connection_name}, f)
+            f.write("\n")
+    except Exception as exc:
+        print(f"Error writing status file {status_file}:", exc)
+        raise
+
+    fscache = FileSystemCache()
+    cached_read = fscache.read
+    errors = Errors(options, read_source=lambda path: read_py_file(path, cached_read))
+
+    ctx = ServerContext(options, disable_error_code, enable_error_code, errors, fscache)
+    try:
+        with server:
+            serve(server, ctx)
+    except (OSError, IPCException) as exc:
+        if options.verbosity >= 1:
+            print("Error communicating with coordinator:", exc)
+    except Exception as exc:
+        report_internal_error(exc, errors.file, 0, errors, options)
+    finally:
+        server.cleanup()
+
+    if options.fast_exit:
+        # Exit fast if allowed, since coordinator is waiting on us.
+        util.hard_exit(0)
+
+
+def serve(server: IPCServer, ctx: ServerContext) -> None:
+    """Main server loop of the worker.
+
+    Receive initial state from the coordinator, then process each
+    SCC checking request and reply to client (coordinator). See module
+    docstring for more details on the protocol.
+    """
+    sources = SourcesDataMessage.read(receive(server)).sources
+    manager = setup_worker_manager(sources, ctx)
+    if manager is None:
+        return
+
+    # Notify coordinator we are done with setup.
+    send(server, AckMessage())
+    graph_data = GraphMessage.read(receive(server), manager)
+    # Update some manager data in-place as it has been passed to semantic analyzer.
+    manager.missing_modules |= graph_data.missing_modules
+    graph = graph_data.graph
+    for id in graph:
+        manager.import_map[id] = graph[id].dependencies_set
+    # Link modules dicts, so that plugins will get access to ASTs as we parse them.
+    manager.plugin.set_modules(manager.modules)
+
+    # Notify coordinator we are ready to receive computed graph SCC structure.
+    send(server, AckMessage())
+    sccs = SccsDataMessage.read(receive(server)).sccs
+    manager.scc_by_id = {scc.id: scc for scc in sccs}
+    manager.top_order = [scc.id for scc in sccs]
+
+    # Notify coordinator we are ready to start processing SCCs.
+    send(server, AckMessage())
+    while True:
+        scc_message = SccRequestMessage.read(receive(server))
+        scc_id = scc_message.scc_id
+        if scc_id is None:
+            manager.dump_stats()
+            break
+        scc = manager.scc_by_id[scc_id]
+        t0 = time.time()
+        try:
+            if platform.python_implementation() == "CPython":
+                # Since we are splitting the GC freeze hack into multiple smaller freezes,
+                # we should collect young generations to not accumulate accidental garbage.
+                gc.collect(generation=1)
+                gc.collect(generation=0)
+                gc.disable()
+            load_states(scc, graph, manager, scc_message.import_errors, scc_message.mod_data)
+            if platform.python_implementation() == "CPython":
+                gc.freeze()
+                gc.unfreeze()
+                gc.enable()
+            result = process_stale_scc(graph, scc, manager, from_cache=graph_data.from_cache)
+            # We must commit after each SCC, otherwise we break --sqlite-cache.
+            manager.metastore.commit()
+        except CompileError as blocker:
+            send(server, SccResponseMessage(scc_id=scc_id, blocker=blocker))
+        else:
+            send(server, SccResponseMessage(scc_id=scc_id, result=result))
+        manager.add_stats(total_process_stale_time=time.time() - t0, stale_sccs_processed=1)
+
+
+def load_states(
+    scc: SCC,
+    graph: Graph,
+    manager: BuildManager,
+    import_errors: dict[str, list[ErrorInfo]],
+    mod_data: dict[str, tuple[bytes, FileRawData | None]],
+) -> None:
+    """Re-create full state of an SCC as it would have been in coordinator."""
+    for id in scc.mod_ids:
+        state = graph[id]
+        # Re-clone options since we don't send them, it is usually faster than deserializing.
+        state.options = state.options.clone_for_module(state.id)
+        suppressed_deps_opts, raw_data = mod_data[id]
+        state.parse_file(raw_data=raw_data)
+        # Set data that is needed to be written to cache meta.
+        state.known_suppressed_deps_opts = suppressed_deps_opts
+        assert state.tree is not None
+        import_lines = {imp.line for imp in state.tree.imports}
+        state.imports_ignored = {
+            line: codes for line, codes in state.tree.ignored_lines.items() if line in import_lines
+        }
+        # Replay original errors encountered during graph loading in coordinator.
+        if id in import_errors:
+            manager.errors.set_file(state.xpath, id, state.options)
+            for err_info in import_errors[id]:
+                manager.errors.add_error_info(err_info)
+
+
+def setup_worker_manager(sources: list[BuildSource], ctx: ServerContext) -> BuildManager | None:
+    data_dir = os.path.dirname(os.path.dirname(__file__))
+    # This is used for testing only now.
+    alt_lib_path = os.environ.get("MYPY_ALT_LIB_PATH")
+    search_paths = compute_search_paths(sources, ctx.options, data_dir, alt_lib_path)
+
+    source_set = BuildSourceSet(sources)
+    try:
+        plugin, snapshot = load_plugins(ctx.options, ctx.errors, sys.stdout, [])
+    except CompileError:
+        # CompileError while importing plugins will be reported by the coordinator.
+        return None
+
+    # Process the rest of the options when plugins are loaded.
+    options = ctx.options
+    options.disable_error_code = ctx.disable_error_code
+    options.enable_error_code = ctx.enable_error_code
+    options.process_error_codes(error_callback=lambda msg: None)
+
+    def flush_errors(filename: str | None, new_messages: list[str], is_serious: bool) -> None:
+        # We never flush errors in the worker, we send them back to coordinator.
+        pass
+
+    return BuildManager(
+        data_dir,
+        search_paths,
+        ignore_prefix=os.getcwd(),
+        source_set=source_set,
+        reports=None,
+        options=options,
+        version_id=__version__,
+        plugin=plugin,
+        plugins_snapshot=snapshot,
+        errors=ctx.errors,
+        error_formatter=None,
+        flush_errors=flush_errors,
+        fscache=ctx.fscache,
+        stdout=sys.stdout,
+        stderr=sys.stderr,
+        parallel_worker=True,
+    )
+
+
+def console_entry() -> None:
+    main(sys.argv[1:])

venv/lib/python3.11/site-packages/mypy/cache.py

@@ -0,0 +1,532 @@
+"""
+This module contains high-level logic for fixed format serialization.
+
+Lower-level parts are implemented in C in mypyc/lib-rt/internal/librt_internal.c
+Short summary of low-level functionality:
+* integers are automatically serialized as 1, 2, or 4 bytes, or arbitrary length.
+* str/bytes are serialized as size (1, 2, or 4 bytes) followed by bytes buffer.
+* floats are serialized as C doubles.
+
+At high-level we add type tags as needed so that our format is self-descriptive.
+More precisely:
+* False, True, and None are stored as just a tag: 0, 1, 2 correspondingly.
+* builtin primitives like int/str/bytes/float are stored as their type tag followed
+  by bare (low-level) representation of the value. Reserved tag range for primitives is
+  3 ... 19.
+* generic (heterogeneous) list are stored as tag, followed by bare size, followed by
+  sequence of tagged values.
+* homogeneous lists of primitives are stored as tag, followed by bare size, followed
+  by sequence of bare values.
+* reserved tag range for sequence-like builtins is 20 ... 29
+* currently we have only one mapping-like format: string-keyed dictionary with heterogeneous
+  values. It is stored as tag, followed by bare size, followed by sequence of pairs: bare
+  string key followed by tagged value.
+* reserved tag range for mapping-like builtins is 30 ... 39
+* there is an additional reserved tag range 40 ... 49 for any other builtin collections.
+* custom classes (like types, symbols etc.) are stored as tag, followed by a sequence of
+  tagged field values, followed by a special end tag 255. Names of class fields are
+  *not* stored, the caller should know the field names and order for the given class tag.
+* reserved tag range for symbols (TypeInfo, Var, etc) is 50 ... 79.
+* class Instance is the only exception from the above format (since it is the most common one).
+  It has two extra formats: few most common instances like "builtins.object" are stored as
+  instance tag followed by a secondary tag, other plain non-generic instances are stored as
+  instance tag followed by secondary tag followed by fullname as bare string. All generic
+  readers must handle these.
+* reserved tag range for Instance type formats is 80 ... 99, for other types it is 100 ... 149.
+* tag 254 is reserved for if we would ever need to extend the tag range to indicated second tag
+  page. Tags 150 ... 253 are free for everything else (e.g. AST nodes etc).
+
+General convention is that custom classes implement write() and read() methods for FF
+serialization. The write method should write both class tag and end tag. The read method
+conventionally *does not* read the start tag (to simplify logic for unions). Known exceptions
+are MypyFile.read() and SymbolTableNode.read(), since those two never appear in a union.
+
+If any of these details change, or if the structure of CacheMeta changes please
+bump CACHE_VERSION below.
+"""
+
+from __future__ import annotations
+
+from collections.abc import Sequence
+from typing import Any, Final, TypeAlias as _TypeAlias
+
+from librt.internal import (
+    ReadBuffer as ReadBuffer,
+    WriteBuffer as WriteBuffer,
+    read_bool as read_bool,
+    read_bytes as read_bytes_bare,
+    read_float as read_float_bare,
+    read_int as read_int_bare,
+    read_str as read_str_bare,
+    read_tag as read_tag,
+    write_bool as write_bool,
+    write_bytes as write_bytes_bare,
+    write_float as write_float_bare,
+    write_int as write_int_bare,
+    write_str as write_str_bare,
+    write_tag as write_tag,
+)
+from mypy_extensions import u8
+
+# High-level cache layout format
+CACHE_VERSION: Final = 7
+
+# Type used internally to represent errors:
+#   (path, line, column, end_line, end_column, severity, message, code)
+ErrorTuple: _TypeAlias = tuple[str | None, int, int, int, int, str, str, str | None]
+
+
+class CacheMeta:
+    """Class representing cache metadata for a module."""
+
+    def __init__(
+        self,
+        *,
+        id: str,
+        path: str,
+        mtime: int,
+        size: int,
+        hash: str,
+        dependencies: list[str],
+        data_mtime: int,
+        data_file: str,
+        suppressed: list[str],
+        imports_ignored: dict[int, list[str]],
+        options: dict[str, object],
+        suppressed_deps_opts: bytes,
+        dep_prios: list[int],
+        dep_lines: list[int],
+        dep_hashes: list[bytes],
+        interface_hash: bytes,
+        trans_dep_hash: bytes,
+        version_id: str,
+        ignore_all: bool,
+        plugin_data: Any,
+    ) -> None:
+        self.id = id
+        self.path = path
+        self.mtime = mtime  # source file mtime
+        self.size = size  # source file size
+        self.hash = hash  # source file hash (as a hex string for historical reasons)
+        self.dependencies = dependencies  # names of imported modules
+        self.data_mtime = data_mtime  # mtime of data_file
+        self.data_file = data_file  # path of <id>.data.json or <id>.data.ff
+        self.suppressed = suppressed  # dependencies that weren't imported
+        self.imports_ignored = imports_ignored  # type ignore codes by line
+        self.options = options  # build options snapshot
+        self.suppressed_deps_opts = suppressed_deps_opts  # hash of import-related options
+        # dep_prios and dep_lines are both aligned with dependencies + suppressed
+        self.dep_prios = dep_prios
+        self.dep_lines = dep_lines
+        # dep_hashes list is aligned with dependencies only
+        self.dep_hashes = dep_hashes  # list of interface_hash for dependencies
+        self.interface_hash = interface_hash  # hash representing the public interface
+        self.trans_dep_hash = trans_dep_hash  # hash of import structure (transitive)
+        self.version_id = version_id  # mypy version for cache invalidation
+        self.ignore_all = ignore_all  # if errors were ignored
+        self.plugin_data = plugin_data  # config data from plugins
+
+    def serialize(self) -> dict[str, Any]:
+        return {
+            "id": self.id,
+            "path": self.path,
+            "mtime": self.mtime,
+            "size": self.size,
+            "hash": self.hash,
+            "data_mtime": self.data_mtime,
+            "dependencies": self.dependencies,
+            "suppressed": self.suppressed,
+            "imports_ignored": {str(line): codes for line, codes in self.imports_ignored.items()},
+            "options": self.options,
+            "suppressed_deps_opts": self.suppressed_deps_opts.hex(),
+            "dep_prios": self.dep_prios,
+            "dep_lines": self.dep_lines,
+            "dep_hashes": [dep.hex() for dep in self.dep_hashes],
+            "interface_hash": self.interface_hash.hex(),
+            "trans_dep_hash": self.trans_dep_hash.hex(),
+            "version_id": self.version_id,
+            "ignore_all": self.ignore_all,
+            "plugin_data": self.plugin_data,
+        }
+
+    @classmethod
+    def deserialize(cls, meta: dict[str, Any], data_file: str) -> CacheMeta | None:
+        try:
+            return CacheMeta(
+                id=meta["id"],
+                path=meta["path"],
+                mtime=meta["mtime"],
+                size=meta["size"],
+                hash=meta["hash"],
+                dependencies=meta["dependencies"],
+                data_mtime=meta["data_mtime"],
+                data_file=data_file,
+                suppressed=meta["suppressed"],
+                imports_ignored={
+                    int(line): codes for line, codes in meta["imports_ignored"].items()
+                },
+                options=meta["options"],
+                suppressed_deps_opts=bytes.fromhex(meta["suppressed_deps_opts"]),
+                dep_prios=meta["dep_prios"],
+                dep_lines=meta["dep_lines"],
+                dep_hashes=[bytes.fromhex(dep) for dep in meta["dep_hashes"]],
+                interface_hash=bytes.fromhex(meta["interface_hash"]),
+                trans_dep_hash=bytes.fromhex(meta["trans_dep_hash"]),
+                version_id=meta["version_id"],
+                ignore_all=meta["ignore_all"],
+                plugin_data=meta["plugin_data"],
+            )
+        except (KeyError, ValueError):
+            return None
+
+    def write(self, data: WriteBuffer) -> None:
+        write_str(data, self.id)
+        write_str(data, self.path)
+        write_int(data, self.mtime)
+        write_int(data, self.size)
+        write_str(data, self.hash)
+        write_str_list(data, self.dependencies)
+        write_int(data, self.data_mtime)
+        write_str_list(data, self.suppressed)
+        write_int_bare(data, len(self.imports_ignored))
+        for line, codes in self.imports_ignored.items():
+            write_int(data, line)
+            write_str_list(data, codes)
+        write_json(data, self.options)
+        write_bytes(data, self.suppressed_deps_opts)
+        write_int_list(data, self.dep_prios)
+        write_int_list(data, self.dep_lines)
+        write_bytes_list(data, self.dep_hashes)
+        write_bytes(data, self.interface_hash)
+        write_bytes(data, self.trans_dep_hash)
+        write_str(data, self.version_id)
+        write_bool(data, self.ignore_all)
+        # Plugin data may be not a dictionary, so we use
+        # a more generic write_json_value() here.
+        write_json_value(data, self.plugin_data)
+
+    @classmethod
+    def read(cls, data: ReadBuffer, data_file: str) -> CacheMeta | None:
+        try:
+            return CacheMeta(
+                id=read_str(data),
+                path=read_str(data),
+                mtime=read_int(data),
+                size=read_int(data),
+                hash=read_str(data),
+                dependencies=read_str_list(data),
+                data_mtime=read_int(data),
+                data_file=data_file,
+                suppressed=read_str_list(data),
+                imports_ignored={
+                    read_int(data): read_str_list(data) for _ in range(read_int_bare(data))
+                },
+                options=read_json(data),
+                suppressed_deps_opts=read_bytes(data),
+                dep_prios=read_int_list(data),
+                dep_lines=read_int_list(data),
+                dep_hashes=read_bytes_list(data),
+                interface_hash=read_bytes(data),
+                trans_dep_hash=read_bytes(data),
+                version_id=read_str(data),
+                ignore_all=read_bool(data),
+                plugin_data=read_json_value(data),
+            )
+        except (ValueError, AssertionError):
+            return None
+
+
+# Always use this type alias to refer to type tags.
+Tag = u8
+
+# Primitives.
+LITERAL_FALSE: Final[Tag] = 0
+LITERAL_TRUE: Final[Tag] = 1
+LITERAL_NONE: Final[Tag] = 2
+LITERAL_INT: Final[Tag] = 3
+LITERAL_STR: Final[Tag] = 4
+LITERAL_BYTES: Final[Tag] = 5
+LITERAL_FLOAT: Final[Tag] = 6
+LITERAL_COMPLEX: Final[Tag] = 7
+
+# Collections.
+LIST_GEN: Final[Tag] = 20
+LIST_INT: Final[Tag] = 21
+LIST_STR: Final[Tag] = 22
+LIST_BYTES: Final[Tag] = 23
+TUPLE_GEN: Final[Tag] = 24
+DICT_STR_GEN: Final[Tag] = 30
+DICT_INT_GEN: Final[Tag] = 31
+
+# Misc classes.
+EXTRA_ATTRS: Final[Tag] = 150
+DT_SPEC: Final[Tag] = 151
+# Four integers representing source file (line, column) range.
+LOCATION: Final[Tag] = 152
+
+END_TAG: Final[Tag] = 255
+
+
+def read_literal(data: ReadBuffer, tag: Tag) -> int | str | bool | float:
+    if tag == LITERAL_INT:
+        return read_int_bare(data)
+    elif tag == LITERAL_STR:
+        return read_str_bare(data)
+    elif tag == LITERAL_FALSE:
+        return False
+    elif tag == LITERAL_TRUE:
+        return True
+    elif tag == LITERAL_FLOAT:
+        return read_float_bare(data)
+    assert False, f"Unknown literal tag {tag}"
+
+
+# There is an intentional asymmetry between read and write for literals because
+# None and/or complex values are only allowed in some contexts but not in others.
+def write_literal(data: WriteBuffer, value: int | str | bool | float | complex | None) -> None:
+    if isinstance(value, bool):
+        write_bool(data, value)
+    elif isinstance(value, int):
+        write_tag(data, LITERAL_INT)
+        write_int_bare(data, value)
+    elif isinstance(value, str):
+        write_tag(data, LITERAL_STR)
+        write_str_bare(data, value)
+    elif isinstance(value, float):
+        write_tag(data, LITERAL_FLOAT)
+        write_float_bare(data, value)
+    elif isinstance(value, complex):
+        write_tag(data, LITERAL_COMPLEX)
+        write_float_bare(data, value.real)
+        write_float_bare(data, value.imag)
+    else:
+        write_tag(data, LITERAL_NONE)
+
+
+def read_int(data: ReadBuffer) -> int:
+    assert read_tag(data) == LITERAL_INT
+    return read_int_bare(data)
+
+
+def write_int(data: WriteBuffer, value: int) -> None:
+    write_tag(data, LITERAL_INT)
+    write_int_bare(data, value)
+
+
+def read_str(data: ReadBuffer) -> str:
+    assert read_tag(data) == LITERAL_STR
+    return read_str_bare(data)
+
+
+def write_str(data: WriteBuffer, value: str) -> None:
+    write_tag(data, LITERAL_STR)
+    write_str_bare(data, value)
+
+
+def read_bytes(data: ReadBuffer) -> bytes:
+    assert read_tag(data) == LITERAL_BYTES
+    return read_bytes_bare(data)
+
+
+def write_bytes(data: WriteBuffer, value: bytes) -> None:
+    write_tag(data, LITERAL_BYTES)
+    write_bytes_bare(data, value)
+
+
+def read_int_opt(data: ReadBuffer) -> int | None:
+    tag = read_tag(data)
+    if tag == LITERAL_NONE:
+        return None
+    assert tag == LITERAL_INT
+    return read_int_bare(data)
+
+
+def write_int_opt(data: WriteBuffer, value: int | None) -> None:
+    if value is not None:
+        write_tag(data, LITERAL_INT)
+        write_int_bare(data, value)
+    else:
+        write_tag(data, LITERAL_NONE)
+
+
+def read_str_opt(data: ReadBuffer) -> str | None:
+    tag = read_tag(data)
+    if tag == LITERAL_NONE:
+        return None
+    assert tag == LITERAL_STR
+    return read_str_bare(data)
+
+
+def write_str_opt(data: WriteBuffer, value: str | None) -> None:
+    if value is not None:
+        write_tag(data, LITERAL_STR)
+        write_str_bare(data, value)
+    else:
+        write_tag(data, LITERAL_NONE)
+
+
+def read_int_list(data: ReadBuffer) -> list[int]:
+    assert read_tag(data) == LIST_INT
+    size = read_int_bare(data)
+    return [read_int_bare(data) for _ in range(size)]
+
+
+def write_int_list(data: WriteBuffer, value: list[int]) -> None:
+    write_tag(data, LIST_INT)
+    write_int_bare(data, len(value))
+    for item in value:
+        write_int_bare(data, item)
+
+
+def read_str_list(data: ReadBuffer) -> list[str]:
+    assert read_tag(data) == LIST_STR
+    size = read_int_bare(data)
+    return [read_str_bare(data) for _ in range(size)]
+
+
+def write_str_list(data: WriteBuffer, value: Sequence[str]) -> None:
+    write_tag(data, LIST_STR)
+    write_int_bare(data, len(value))
+    for item in value:
+        write_str_bare(data, item)
+
+
+def read_bytes_list(data: ReadBuffer) -> list[bytes]:
+    assert read_tag(data) == LIST_BYTES
+    size = read_int_bare(data)
+    return [read_bytes_bare(data) for _ in range(size)]
+
+
+def write_bytes_list(data: WriteBuffer, value: Sequence[bytes]) -> None:
+    write_tag(data, LIST_BYTES)
+    write_int_bare(data, len(value))
+    for item in value:
+        write_bytes_bare(data, item)
+
+
+def read_str_opt_list(data: ReadBuffer) -> list[str | None]:
+    assert read_tag(data) == LIST_GEN
+    size = read_int_bare(data)
+    return [read_str_opt(data) for _ in range(size)]
+
+
+def write_str_opt_list(data: WriteBuffer, value: list[str | None]) -> None:
+    write_tag(data, LIST_GEN)
+    write_int_bare(data, len(value))
+    for item in value:
+        write_str_opt(data, item)
+
+
+Value: _TypeAlias = None | int | str | bool
+
+# Our JSON format is somewhat non-standard as we distinguish lists and tuples.
+# This is convenient for some internal things, like mypyc plugin and error serialization.
+JsonValue: _TypeAlias = (
+    Value | list["JsonValue"] | dict[str, "JsonValue"] | tuple["JsonValue", ...]
+)
+
+
+def read_json_value(data: ReadBuffer) -> JsonValue:
+    tag = read_tag(data)
+    if tag == LITERAL_NONE:
+        return None
+    if tag == LITERAL_FALSE:
+        return False
+    if tag == LITERAL_TRUE:
+        return True
+    if tag == LITERAL_INT:
+        return read_int_bare(data)
+    if tag == LITERAL_STR:
+        return read_str_bare(data)
+    if tag == LIST_GEN:
+        size = read_int_bare(data)
+        return [read_json_value(data) for _ in range(size)]
+    if tag == TUPLE_GEN:
+        size = read_int_bare(data)
+        return tuple(read_json_value(data) for _ in range(size))
+    if tag == DICT_STR_GEN:
+        size = read_int_bare(data)
+        return {read_str_bare(data): read_json_value(data) for _ in range(size)}
+    assert False, f"Invalid JSON tag: {tag}"
+
+
+def write_json_value(data: WriteBuffer, value: JsonValue) -> None:
+    if value is None:
+        write_tag(data, LITERAL_NONE)
+    elif isinstance(value, bool):
+        write_bool(data, value)
+    elif isinstance(value, int):
+        write_tag(data, LITERAL_INT)
+        write_int_bare(data, value)
+    elif isinstance(value, str):
+        write_tag(data, LITERAL_STR)
+        write_str_bare(data, value)
+    elif isinstance(value, list):
+        write_tag(data, LIST_GEN)
+        write_int_bare(data, len(value))
+        for val in value:
+            write_json_value(data, val)
+    elif isinstance(value, tuple):
+        write_tag(data, TUPLE_GEN)
+        write_int_bare(data, len(value))
+        for val in value:
+            write_json_value(data, val)
+    elif isinstance(value, dict):
+        write_tag(data, DICT_STR_GEN)
+        write_int_bare(data, len(value))
+        for key in sorted(value):
+            write_str_bare(data, key)
+            write_json_value(data, value[key])
+    else:
+        assert False, f"Invalid JSON value: {value}"
+
+
+# These are functions for JSON *dictionaries* specifically. Unfortunately, we
+# must use imprecise types here, because the callers use imprecise types.
+def read_json(data: ReadBuffer) -> dict[str, Any]:
+    assert read_tag(data) == DICT_STR_GEN
+    size = read_int_bare(data)
+    return {read_str_bare(data): read_json_value(data) for _ in range(size)}
+
+
+def write_json(data: WriteBuffer, value: dict[str, Any]) -> None:
+    write_tag(data, DICT_STR_GEN)
+    write_int_bare(data, len(value))
+    for key in sorted(value):
+        write_str_bare(data, key)
+        write_json_value(data, value[key])
+
+
+def write_errors(data: WriteBuffer, errs: list[ErrorTuple]) -> None:
+    write_tag(data, LIST_GEN)
+    write_int_bare(data, len(errs))
+    for path, line, column, end_line, end_column, severity, message, code in errs:
+        write_tag(data, TUPLE_GEN)
+        write_str_opt(data, path)
+        write_int(data, line)
+        write_int(data, column)
+        write_int(data, end_line)
+        write_int(data, end_column)
+        write_str(data, severity)
+        write_str(data, message)
+        write_str_opt(data, code)
+
+
+def read_errors(data: ReadBuffer) -> list[ErrorTuple]:
+    assert read_tag(data) == LIST_GEN
+    result = []
+    for _ in range(read_int_bare(data)):
+        assert read_tag(data) == TUPLE_GEN
+        result.append(
+            (
+                read_str_opt(data),
+                read_int(data),
+                read_int(data),
+                read_int(data),
+                read_int(data),
+                read_str(data),
+                read_str(data),
+                read_str_opt(data),
+            )
+        )
+    return result

venv/lib/python3.11/site-packages/mypy/checker_shared.py

@@ -0,0 +1,365 @@
+"""Shared definitions used by different parts of type checker."""
+
+from __future__ import annotations
+
+from abc import abstractmethod
+from collections.abc import Iterator, Sequence, Set as AbstractSet
+from contextlib import contextmanager
+from typing import NamedTuple, overload
+
+from mypy_extensions import trait
+
+from mypy.errorcodes import ErrorCode
+from mypy.errors import ErrorWatcher
+from mypy.message_registry import ErrorMessage
+from mypy.nodes import (
+    ArgKind,
+    Context,
+    Expression,
+    FuncItem,
+    LambdaExpr,
+    MypyFile,
+    Node,
+    RefExpr,
+    SymbolNode,
+    TypeInfo,
+    Var,
+)
+from mypy.plugin import CheckerPluginInterface, Plugin
+from mypy.types import (
+    CallableType,
+    Instance,
+    LiteralValue,
+    Overloaded,
+    PartialType,
+    TupleType,
+    Type,
+    TypedDictType,
+    TypeType,
+)
+from mypy.typevars import fill_typevars
+
+
+# An object that represents either a precise type or a type with an upper bound;
+# it is important for correct type inference with isinstance.
+class TypeRange(NamedTuple):
+    item: Type
+    is_upper_bound: bool  # False => precise type
+
+
+@trait
+class ExpressionCheckerSharedApi:
+    @abstractmethod
+    def accept(
+        self,
+        node: Expression,
+        type_context: Type | None = None,
+        allow_none_return: bool = False,
+        always_allow_any: bool = False,
+        is_callee: bool = False,
+    ) -> Type:
+        raise NotImplementedError
+
+    @abstractmethod
+    def analyze_ref_expr(self, e: RefExpr, lvalue: bool = False) -> Type:
+        raise NotImplementedError
+
+    @abstractmethod
+    def check_call(
+        self,
+        callee: Type,
+        args: list[Expression],
+        arg_kinds: list[ArgKind],
+        context: Context,
+        arg_names: Sequence[str | None] | None = None,
+        callable_node: Expression | None = None,
+        callable_name: str | None = None,
+        object_type: Type | None = None,
+        original_type: Type | None = None,
+    ) -> tuple[Type, Type]:
+        raise NotImplementedError
+
+    @abstractmethod
+    def transform_callee_type(
+        self,
+        callable_name: str | None,
+        callee: Type,
+        args: list[Expression],
+        arg_kinds: list[ArgKind],
+        context: Context,
+        arg_names: Sequence[str | None] | None = None,
+        object_type: Type | None = None,
+    ) -> Type:
+        raise NotImplementedError
+
+    @abstractmethod
+    def method_fullname(self, object_type: Type, method_name: str) -> str | None:
+        raise NotImplementedError
+
+    @abstractmethod
+    def check_method_call_by_name(
+        self,
+        method: str,
+        base_type: Type,
+        args: list[Expression],
+        arg_kinds: list[ArgKind],
+        context: Context,
+        original_type: Type | None = None,
+    ) -> tuple[Type, Type]:
+        raise NotImplementedError
+
+    @abstractmethod
+    def visit_typeddict_index_expr(
+        self, td_type: TypedDictType, index: Expression, setitem: bool = False
+    ) -> tuple[Type, set[str]]:
+        raise NotImplementedError
+
+    @abstractmethod
+    def infer_literal_expr_type(self, value: LiteralValue, fallback_name: str) -> Type:
+        raise NotImplementedError
+
+    @abstractmethod
+    def analyze_static_reference(
+        self,
+        node: SymbolNode,
+        ctx: Context,
+        is_lvalue: bool,
+        *,
+        include_modules: bool = True,
+        suppress_errors: bool = False,
+    ) -> Type:
+        raise NotImplementedError
+
+
+@trait
+class TypeCheckerSharedApi(CheckerPluginInterface):
+    plugin: Plugin
+    module_refs: set[str]
+    scope: CheckerScope
+    checking_missing_await: bool
+    allow_constructor_cache: bool
+
+    @property
+    @abstractmethod
+    def expr_checker(self) -> ExpressionCheckerSharedApi:
+        raise NotImplementedError
+
+    @abstractmethod
+    def named_type(self, name: str) -> Instance:
+        raise NotImplementedError
+
+    @abstractmethod
+    def lookup_typeinfo(self, fullname: str) -> TypeInfo:
+        raise NotImplementedError
+
+    @abstractmethod
+    def lookup_type(self, node: Expression) -> Type:
+        raise NotImplementedError
+
+    @abstractmethod
+    def handle_cannot_determine_type(self, name: str, context: Context) -> None:
+        raise NotImplementedError
+
+    @abstractmethod
+    def handle_partial_var_type(
+        self, typ: PartialType, is_lvalue: bool, node: Var, context: Context
+    ) -> Type:
+        raise NotImplementedError
+
+    @overload
+    @abstractmethod
+    def check_subtype(
+        self,
+        subtype: Type,
+        supertype: Type,
+        context: Context,
+        msg: str,
+        subtype_label: str | None = None,
+        supertype_label: str | None = None,
+        *,
+        notes: list[str] | None = None,
+        code: ErrorCode | None = None,
+        outer_context: Context | None = None,
+    ) -> bool: ...
+
+    @overload
+    @abstractmethod
+    def check_subtype(
+        self,
+        subtype: Type,
+        supertype: Type,
+        context: Context,
+        msg: ErrorMessage,
+        subtype_label: str | None = None,
+        supertype_label: str | None = None,
+        *,
+        notes: list[str] | None = None,
+        outer_context: Context | None = None,
+    ) -> bool: ...
+
+    # Unfortunately, mypyc doesn't support abstract overloads yet.
+    @abstractmethod
+    def check_subtype(
+        self,
+        subtype: Type,
+        supertype: Type,
+        context: Context,
+        msg: str | ErrorMessage,
+        subtype_label: str | None = None,
+        supertype_label: str | None = None,
+        *,
+        notes: list[str] | None = None,
+        code: ErrorCode | None = None,
+        outer_context: Context | None = None,
+    ) -> bool:
+        raise NotImplementedError
+
+    @abstractmethod
+    def get_final_context(self) -> bool:
+        raise NotImplementedError
+
+    @overload
+    @abstractmethod
+    def conditional_types_with_intersection(
+        self,
+        expr_type: Type,
+        type_ranges: list[TypeRange] | None,
+        ctx: Context,
+        default: None = None,
+    ) -> tuple[Type | None, Type | None]: ...
+
+    @overload
+    @abstractmethod
+    def conditional_types_with_intersection(
+        self, expr_type: Type, type_ranges: list[TypeRange] | None, ctx: Context, default: Type
+    ) -> tuple[Type, Type]: ...
+
+    # Unfortunately, mypyc doesn't support abstract overloads yet.
+    @abstractmethod
+    def conditional_types_with_intersection(
+        self,
+        expr_type: Type,
+        type_ranges: list[TypeRange] | None,
+        ctx: Context,
+        default: Type | None = None,
+    ) -> tuple[Type | None, Type | None]:
+        raise NotImplementedError
+
+    @abstractmethod
+    def narrow_type_by_identity_equality(
+        self,
+        operator: str,
+        operands: list[Expression],
+        operand_types: list[Type],
+        expr_indices: list[int],
+        narrowable_indices: AbstractSet[int],
+    ) -> tuple[dict[Expression, Type] | None, dict[Expression, Type] | None]:
+        raise NotImplementedError
+
+    @abstractmethod
+    def check_deprecated(self, node: Node | None, context: Context) -> None:
+        raise NotImplementedError
+
+    @abstractmethod
+    def warn_deprecated(self, node: Node | None, context: Context) -> None:
+        raise NotImplementedError
+
+    @abstractmethod
+    def type_is_iterable(self, type: Type) -> bool:
+        raise NotImplementedError
+
+    @abstractmethod
+    def iterable_item_type(
+        self, it: Instance | CallableType | TypeType | Overloaded, context: Context
+    ) -> Type:
+        raise NotImplementedError
+
+    @abstractmethod
+    @contextmanager
+    def checking_await_set(self) -> Iterator[None]:
+        raise NotImplementedError
+
+    @abstractmethod
+    def get_precise_awaitable_type(self, typ: Type, local_errors: ErrorWatcher) -> Type | None:
+        raise NotImplementedError
+
+    @abstractmethod
+    def add_any_attribute_to_type(self, typ: Type, name: str) -> Type:
+        raise NotImplementedError
+
+    @abstractmethod
+    def is_defined_in_stub(self, typ: Instance, /) -> bool:
+        raise NotImplementedError
+
+
+class CheckerScope:
+    # We keep two stacks combined, to maintain the relative order
+    stack: list[TypeInfo | FuncItem | MypyFile]
+
+    def __init__(self, module: MypyFile) -> None:
+        self.stack = [module]
+
+    def current_function(self) -> FuncItem | None:
+        for e in reversed(self.stack):
+            if isinstance(e, FuncItem):
+                return e
+        return None
+
+    def top_level_function(self) -> FuncItem | None:
+        """Return top-level non-lambda function."""
+        for e in self.stack:
+            if isinstance(e, FuncItem) and not isinstance(e, LambdaExpr):
+                return e
+        return None
+
+    def active_class(self) -> TypeInfo | None:
+        if isinstance(self.stack[-1], TypeInfo):
+            return self.stack[-1]
+        return None
+
+    def enclosing_class(self, func: FuncItem | None = None) -> TypeInfo | None:
+        """Is there a class *directly* enclosing this function?"""
+        func = func or self.current_function()
+        assert func, "This method must be called from inside a function"
+        index = self.stack.index(func)
+        assert index, "CheckerScope stack must always start with a module"
+        enclosing = self.stack[index - 1]
+        if isinstance(enclosing, TypeInfo):
+            return enclosing
+        return None
+
+    def active_self_type(self) -> Instance | TupleType | None:
+        """An instance or tuple type representing the current class.
+
+        This returns None unless we are in class body or in a method.
+        In particular, inside a function nested in method this returns None.
+        """
+        info = self.active_class()
+        if not info and self.current_function():
+            info = self.enclosing_class()
+        if info:
+            return fill_typevars(info)
+        return None
+
+    def current_self_type(self) -> Instance | TupleType | None:
+        """Same as active_self_type() but handle functions nested in methods."""
+        for item in reversed(self.stack):
+            if isinstance(item, TypeInfo):
+                return fill_typevars(item)
+        return None
+
+    def is_top_level(self) -> bool:
+        """Is current scope top-level (no classes or functions)?"""
+        return len(self.stack) == 1
+
+    @contextmanager
+    def push_function(self, item: FuncItem) -> Iterator[None]:
+        self.stack.append(item)
+        yield
+        self.stack.pop()
+
+    @contextmanager
+    def push_class(self, info: TypeInfo) -> Iterator[None]:
+        self.stack.append(info)
+        yield
+        self.stack.pop()

venv/lib/python3.11/site-packages/mypy/checker_state.py

@@ -0,0 +1,30 @@
+from __future__ import annotations
+
+from collections.abc import Iterator
+from contextlib import contextmanager
+from typing import Final
+
+from mypy.checker_shared import TypeCheckerSharedApi
+
+# This is global mutable state. Don't add anything here unless there's a very
+# good reason.
+
+
+class TypeCheckerState:
+    # Wrap this in a class since it's faster that using a module-level attribute.
+
+    def __init__(self, type_checker: TypeCheckerSharedApi | None) -> None:
+        # Value varies by file being processed
+        self.type_checker = type_checker
+
+    @contextmanager
+    def set(self, value: TypeCheckerSharedApi) -> Iterator[None]:
+        saved = self.type_checker
+        self.type_checker = value
+        try:
+            yield
+        finally:
+            self.type_checker = saved
+
+
+checker_state: Final = TypeCheckerState(type_checker=None)

venv/lib/python3.11/site-packages/mypy/checkpattern.py

@@ -0,0 +1,885 @@
+"""Pattern checker. This file is conceptually part of TypeChecker."""
+
+from __future__ import annotations
+
+from collections import defaultdict
+from typing import Final, NamedTuple
+
+from mypy import message_registry
+from mypy.checker_shared import TypeCheckerSharedApi, TypeRange
+from mypy.checkmember import analyze_member_access
+from mypy.expandtype import expand_type_by_instance
+from mypy.join import join_types
+from mypy.literals import literal_hash
+from mypy.maptype import map_instance_to_supertype
+from mypy.meet import narrow_declared_type
+from mypy.messages import MessageBuilder
+from mypy.nodes import ARG_POS, Expression, NameExpr, TempNode, TypeAlias, Var
+from mypy.options import Options
+from mypy.patterns import (
+    AsPattern,
+    ClassPattern,
+    MappingPattern,
+    OrPattern,
+    Pattern,
+    SequencePattern,
+    SingletonPattern,
+    StarredPattern,
+    ValuePattern,
+)
+from mypy.plugin import Plugin
+from mypy.subtypes import is_subtype
+from mypy.typeops import (
+    coerce_to_literal,
+    make_simplified_union,
+    try_getting_str_literals_from_type,
+    tuple_fallback,
+)
+from mypy.types import (
+    AnyType,
+    FunctionLike,
+    Instance,
+    NoneType,
+    ProperType,
+    TupleType,
+    Type,
+    TypedDictType,
+    TypeOfAny,
+    TypeType,
+    TypeVarTupleType,
+    TypeVarType,
+    UninhabitedType,
+    UnionType,
+    UnpackType,
+    callable_with_ellipsis,
+    find_unpack_in_list,
+    get_proper_type,
+    split_with_prefix_and_suffix,
+)
+from mypy.typevars import fill_typevars, fill_typevars_with_any
+from mypy.visitor import PatternVisitor
+
+self_match_type_names: Final = [
+    "builtins.bool",
+    "builtins.bytearray",
+    "builtins.bytes",
+    "builtins.dict",
+    "builtins.float",
+    "builtins.frozenset",
+    "builtins.int",
+    "builtins.list",
+    "builtins.set",
+    "builtins.str",
+    "builtins.tuple",
+]
+
+non_sequence_match_type_names: Final = ["builtins.str", "builtins.bytes", "builtins.bytearray"]
+
+
+# For every Pattern a PatternType can be calculated. This requires recursively calculating
+# the PatternTypes of the sub-patterns first.
+# Using the data in the PatternType the match subject and captured names can be narrowed/inferred.
+class PatternType(NamedTuple):
+    type: Type  # The type the match subject can be narrowed to
+    rest_type: Type  # The remaining type if the pattern didn't match
+    captures: dict[Expression, Type]  # The variables captured by the pattern
+
+
+class PatternChecker(PatternVisitor[PatternType]):
+    """Pattern checker.
+
+    This class checks if a pattern can match a type, what the type can be narrowed to, and what
+    type capture patterns should be inferred as.
+    """
+
+    # Some services are provided by a TypeChecker instance.
+    chk: TypeCheckerSharedApi
+    # This is shared with TypeChecker, but stored also here for convenience.
+    msg: MessageBuilder
+    # Currently unused
+    plugin: Plugin
+    # The expression being matched against the pattern
+    subject: Expression
+
+    subject_type: Type
+    # Type of the subject to check the (sub)pattern against
+    type_context: list[Type]
+    # Types that match against self instead of their __match_args__ if used as a class pattern
+    # Filled in from self_match_type_names
+    self_match_types: list[Type]
+    # Types that are sequences, but don't match sequence patterns. Filled in from
+    # non_sequence_match_type_names
+    non_sequence_match_types: list[Type]
+
+    options: Options
+
+    def __init__(
+        self, chk: TypeCheckerSharedApi, msg: MessageBuilder, plugin: Plugin, options: Options
+    ) -> None:
+        self.chk = chk
+        self.msg = msg
+        self.plugin = plugin
+
+        self.type_context = []
+        self.self_match_types = self.generate_types_from_names(self_match_type_names)
+        self.non_sequence_match_types = self.generate_types_from_names(
+            non_sequence_match_type_names
+        )
+        self.options = options
+
+    def accept(self, o: Pattern, type_context: Type) -> PatternType:
+        self.type_context.append(type_context)
+        result = o.accept(self)
+        self.type_context.pop()
+
+        return result
+
+    def visit_as_pattern(self, o: AsPattern) -> PatternType:
+        current_type = self.type_context[-1]
+        if o.pattern is not None:
+            pattern_type = self.accept(o.pattern, current_type)
+            typ, rest_type, type_map = pattern_type
+        else:
+            typ, rest_type, type_map = current_type, UninhabitedType(), {}
+
+        if not is_uninhabited(typ) and o.name is not None:
+            typ, _ = self.chk.conditional_types_with_intersection(
+                current_type, [get_type_range(typ)], o, default=current_type
+            )
+            if not is_uninhabited(typ):
+                type_map[o.name] = typ
+
+        return PatternType(typ, rest_type, type_map)
+
+    def visit_or_pattern(self, o: OrPattern) -> PatternType:
+        current_type = self.type_context[-1]
+
+        #
+        # Check all the subpatterns
+        #
+        pattern_types = []
+        for pattern in o.patterns:
+            pattern_type = self.accept(pattern, current_type)
+            pattern_types.append(pattern_type)
+            if not is_uninhabited(pattern_type.type):
+                current_type = pattern_type.rest_type
+
+        #
+        # Collect the final type
+        #
+        types = []
+        for pattern_type in pattern_types:
+            if not is_uninhabited(pattern_type.type):
+                types.append(pattern_type.type)
+
+        #
+        # Check the capture types
+        #
+        capture_types: dict[Var, list[tuple[Expression, Type]]] = defaultdict(list)
+        # Collect captures from the first subpattern
+        for expr, typ in pattern_types[0].captures.items():
+            node = get_var(expr)
+            capture_types[node].append((expr, typ))
+
+        # Check if other subpatterns capture the same names
+        for i, pattern_type in enumerate(pattern_types[1:]):
+            vars = {get_var(expr) for expr, _ in pattern_type.captures.items()}
+            if capture_types.keys() != vars:
+                self.msg.fail(message_registry.OR_PATTERN_ALTERNATIVE_NAMES, o.patterns[i])
+            for expr, typ in pattern_type.captures.items():
+                node = get_var(expr)
+                capture_types[node].append((expr, typ))
+
+        captures: dict[Expression, Type] = {}
+        for capture_list in capture_types.values():
+            typ = UninhabitedType()
+            for _, other in capture_list:
+                typ = make_simplified_union([typ, other])
+
+            captures[capture_list[0][0]] = typ
+
+        union_type = make_simplified_union(types)
+        return PatternType(union_type, current_type, captures)
+
+    def visit_value_pattern(self, o: ValuePattern) -> PatternType:
+        current_type = self.type_context[-1]
+        typ = self.chk.expr_checker.accept(o.expr)
+        typ = coerce_to_literal(typ)
+        node = TempNode(current_type)
+        # Value patterns are essentially a syntactic sugar on top of `if x == Value`.
+        # They should be treated equivalently.
+        ok_map, rest_map = self.chk.narrow_type_by_identity_equality(
+            "==", [node, TempNode(typ)], [current_type, typ], [0, 1], {0}
+        )
+        ok_type = ok_map.get(node, current_type) if ok_map is not None else UninhabitedType()
+        rest_type = rest_map.get(node, current_type) if rest_map is not None else UninhabitedType()
+        return PatternType(ok_type, rest_type, {})
+
+    def visit_singleton_pattern(self, o: SingletonPattern) -> PatternType:
+        current_type = self.type_context[-1]
+        value: bool | None = o.value
+        if isinstance(value, bool):
+            typ = self.chk.expr_checker.infer_literal_expr_type(value, "builtins.bool")
+        elif value is None:
+            typ = NoneType()
+        else:
+            assert False
+
+        narrowed_type, rest_type = self.chk.conditional_types_with_intersection(
+            current_type, [get_type_range(typ)], o, default=current_type
+        )
+        return PatternType(narrowed_type, rest_type, {})
+
+    def visit_sequence_pattern(self, o: SequencePattern) -> PatternType:
+        #
+        # Step 1. Check for existence of a starred pattern
+        #
+        current_type = get_proper_type(self.type_context[-1])
+        if not self.can_match_sequence(current_type):
+            return self.early_non_match()
+
+        star_positions = [i for i, p in enumerate(o.patterns) if isinstance(p, StarredPattern)]
+        star_position: int | None = None
+        if len(star_positions) == 1:
+            star_position = star_positions[0]
+        elif len(star_positions) >= 2:
+            assert False, "Parser should prevent multiple starred patterns"
+        required_patterns = len(o.patterns)
+        if star_position is not None:
+            required_patterns -= 1
+
+        #
+        # Step 2. If we have a union, recurse and return the combined result
+        #
+        if isinstance(current_type, UnionType):
+            match_types: list[Type] = []
+            rest_types: list[Type] = []
+            captures_list: dict[Expression, list[Type]] = {}
+
+            if star_position is not None:
+                star_pattern = o.patterns[star_position]
+                assert isinstance(star_pattern, StarredPattern)
+                star_expr = star_pattern.capture
+            else:
+                star_expr = None
+
+            for t in current_type.items:
+                match_type, rest_type, captures = self.accept(o, t)
+                match_types.append(match_type)
+                rest_types.append(rest_type)
+                if not is_uninhabited(match_type):
+                    for expr, typ in captures.items():
+                        p_typ = get_proper_type(typ)
+                        if expr not in captures_list:
+                            captures_list[expr] = []
+                        # Avoid adding in a list[Never] for empty list captures
+                        if (
+                            expr == star_expr
+                            and isinstance(p_typ, Instance)
+                            and p_typ.type.fullname == "builtins.list"
+                            and is_uninhabited(p_typ.args[0])
+                        ):
+                            continue
+                        captures_list[expr].append(typ)
+
+            return PatternType(
+                make_simplified_union(match_types),
+                make_simplified_union(rest_types),
+                {expr: make_simplified_union(types) for expr, types in captures_list.items()},
+            )
+
+        #
+        # Step 3. Get inner types of original type
+        #
+        unpack_index = None
+        if isinstance(current_type, TupleType):
+            inner_types: list[Type] = current_type.items
+            unpack_index = find_unpack_in_list(inner_types)
+            if unpack_index is None:
+                size_diff = len(inner_types) - required_patterns
+                if size_diff < 0:
+                    return self.early_non_match()
+                elif size_diff > 0 and star_position is None:
+                    return self.early_non_match()
+            else:
+                normalized_inner_types = []
+                for it in inner_types:
+                    # Unfortunately, it is not possible to "split" the TypeVarTuple
+                    # into individual items, so we just use its upper bound for the whole
+                    # analysis instead.
+                    if isinstance(it, UnpackType) and isinstance(it.type, TypeVarTupleType):
+                        it = UnpackType(it.type.upper_bound)
+                    normalized_inner_types.append(it)
+                inner_types = normalized_inner_types
+                current_type = current_type.copy_modified(items=normalized_inner_types)
+                if len(inner_types) - 1 > required_patterns and star_position is None:
+                    return self.early_non_match()
+        elif isinstance(current_type, AnyType):
+            inner_type = AnyType(TypeOfAny.from_another_any, current_type)
+            inner_types = [inner_type] * len(o.patterns)
+        elif isinstance(current_type, Instance) and self.chk.type_is_iterable(current_type):
+            inner_type = self.chk.iterable_item_type(current_type, o)
+            inner_types = [inner_type] * len(o.patterns)
+        else:
+            inner_type = self.chk.named_type("builtins.object")
+            inner_types = [inner_type] * len(o.patterns)
+
+        #
+        # Step 4. Match inner patterns
+        #
+        contracted_new_inner_types: list[Type] = []
+        contracted_rest_inner_types: list[Type] = []
+        captures = {}  # dict[Expression, Type]
+
+        contracted_inner_types = self.contract_starred_pattern_types(
+            inner_types, star_position, required_patterns
+        )
+        for p, t in zip(o.patterns, contracted_inner_types):
+            pattern_type = self.accept(p, t)
+            typ, rest, type_map = pattern_type
+            contracted_new_inner_types.append(typ)
+            contracted_rest_inner_types.append(rest)
+            self.update_type_map(captures, type_map)
+
+        new_inner_types = self.expand_starred_pattern_types(
+            contracted_new_inner_types, star_position, len(inner_types), unpack_index is not None
+        )
+        rest_inner_types = self.expand_starred_pattern_types(
+            contracted_rest_inner_types, star_position, len(inner_types), unpack_index is not None
+        )
+
+        #
+        # Step 5. Calculate new type
+        #
+        new_type: Type
+        rest_type = current_type
+        if isinstance(current_type, TupleType) and unpack_index is None:
+            if any(is_uninhabited(typ) for typ in new_inner_types):
+                new_type = UninhabitedType()
+            else:
+                new_type = TupleType(new_inner_types, current_type.partial_fallback)
+
+            num_always_match = sum(is_uninhabited(typ) for typ in rest_inner_types)
+            if num_always_match == len(rest_inner_types):
+                # All subpatterns always match, so we can apply negative narrowing
+                rest_type = UninhabitedType()
+            elif num_always_match == len(rest_inner_types) - 1:
+                # Exactly one subpattern may conditionally match, the rest always match.
+                # We can apply negative narrowing to this one position.
+                rest_type = TupleType(
+                    [
+                        curr if is_uninhabited(rest) else rest
+                        for curr, rest in zip(inner_types, rest_inner_types)
+                    ],
+                    current_type.partial_fallback,
+                )
+        elif isinstance(current_type, TupleType):
+            # For variadic tuples it is too tricky to match individual items like for fixed
+            # tuples, so we instead try to narrow the entire type.
+            # TODO: use more precise narrowing when possible (e.g. for identical shapes).
+            new_tuple_type = TupleType(new_inner_types, current_type.partial_fallback)
+            new_type, _ = self.chk.conditional_types_with_intersection(
+                new_tuple_type, [get_type_range(current_type)], o, default=new_tuple_type
+            )
+            if (
+                star_position is not None
+                and required_patterns <= len(inner_types) - 1
+                and all(is_uninhabited(rest) for rest in rest_inner_types)
+            ):
+                rest_type = UninhabitedType()
+        else:
+            new_inner_type = UninhabitedType()
+            for typ in new_inner_types:
+                new_inner_type = join_types(new_inner_type, typ)
+            new_type = self.construct_sequence_child(current_type, new_inner_type)
+            new_type, possible_rest_type = self.chk.conditional_types_with_intersection(
+                current_type, [get_type_range(new_type)], o, default=current_type
+            )
+            if star_position is not None and len(o.patterns) == 1:
+                # Match cannot be refuted, so narrow the remaining type
+                rest_type = possible_rest_type
+
+        return PatternType(new_type, rest_type, captures)
+
+    def contract_starred_pattern_types(
+        self, types: list[Type], star_pos: int | None, num_patterns: int
+    ) -> list[Type]:
+        """
+        Contracts a list of types in a sequence pattern depending on the position of a starred
+        capture pattern.
+
+        For example if the sequence pattern [a, *b, c] is matched against types [bool, int, str,
+        bytes] the contracted types are [bool, Union[int, str], bytes].
+
+        If star_pos in None the types are returned unchanged.
+        """
+        unpack_index = find_unpack_in_list(types)
+        if unpack_index is not None:
+            # Variadic tuples require "re-shaping" to match the requested pattern.
+            unpack = types[unpack_index]
+            assert isinstance(unpack, UnpackType)
+            unpacked = get_proper_type(unpack.type)
+            # This should be guaranteed by the normalization in the caller.
+            assert isinstance(unpacked, Instance) and unpacked.type.fullname == "builtins.tuple"
+            if star_pos is None:
+                missing = num_patterns - len(types) + 1
+                new_types = types[:unpack_index]
+                new_types += [unpacked.args[0]] * missing
+                new_types += types[unpack_index + 1 :]
+                return new_types
+            prefix, middle, suffix = split_with_prefix_and_suffix(
+                tuple([UnpackType(unpacked) if isinstance(t, UnpackType) else t for t in types]),
+                star_pos,
+                num_patterns - star_pos,
+            )
+            new_middle = []
+            for m in middle:
+                # The existing code expects the star item type, rather than the type of
+                # the whole tuple "slice".
+                if isinstance(m, UnpackType):
+                    new_middle.append(unpacked.args[0])
+                else:
+                    new_middle.append(m)
+            return list(prefix) + [make_simplified_union(new_middle)] + list(suffix)
+        else:
+            if star_pos is None:
+                return types
+            new_types = types[:star_pos]
+            star_length = len(types) - num_patterns
+            new_types.append(make_simplified_union(types[star_pos : star_pos + star_length]))
+            new_types += types[star_pos + star_length :]
+            return new_types
+
+    def expand_starred_pattern_types(
+        self, types: list[Type], star_pos: int | None, num_types: int, original_unpack: bool
+    ) -> list[Type]:
+        """Undoes the contraction done by contract_starred_pattern_types.
+
+        For example if the sequence pattern is [a, *b, c] and types [bool, int, str] are extended
+        to length 4 the result is [bool, int, int, str].
+        """
+        if star_pos is None:
+            return types
+        if original_unpack:
+            # In the case where original tuple type has an unpack item, it is not practical
+            # to coerce pattern type back to the original shape (and may not even be possible),
+            # so we only restore the type of the star item.
+            res = []
+            for i, t in enumerate(types):
+                if i != star_pos or is_uninhabited(t):
+                    res.append(t)
+                else:
+                    res.append(UnpackType(self.chk.named_generic_type("builtins.tuple", [t])))
+            return res
+        new_types = types[:star_pos]
+        star_length = num_types - len(types) + 1
+        new_types += [types[star_pos]] * star_length
+        new_types += types[star_pos + 1 :]
+
+        return new_types
+
+    def visit_starred_pattern(self, o: StarredPattern) -> PatternType:
+        captures: dict[Expression, Type] = {}
+        if o.capture is not None:
+            list_type = self.chk.named_generic_type("builtins.list", [self.type_context[-1]])
+            captures[o.capture] = list_type
+        return PatternType(self.type_context[-1], UninhabitedType(), captures)
+
+    def visit_mapping_pattern(self, o: MappingPattern) -> PatternType:
+        current_type = get_proper_type(self.type_context[-1])
+        can_match = True
+        captures: dict[Expression, Type] = {}
+        for key, value in zip(o.keys, o.values):
+            inner_type = self.get_mapping_item_type(o, current_type, key)
+            if inner_type is None:
+                can_match = False
+                inner_type = self.chk.named_type("builtins.object")
+            pattern_type = self.accept(value, inner_type)
+            if is_uninhabited(pattern_type.type):
+                can_match = False
+            else:
+                self.update_type_map(captures, pattern_type.captures)
+
+        if o.rest is not None:
+            mapping = self.chk.named_type("typing.Mapping")
+            if is_subtype(current_type, mapping) and isinstance(current_type, Instance):
+                mapping_inst = map_instance_to_supertype(current_type, mapping.type)
+                dict_typeinfo = self.chk.lookup_typeinfo("builtins.dict")
+                rest_type = Instance(dict_typeinfo, mapping_inst.args)
+            else:
+                object_type = self.chk.named_type("builtins.object")
+                rest_type = self.chk.named_generic_type(
+                    "builtins.dict", [object_type, object_type]
+                )
+
+            captures[o.rest] = rest_type
+
+        else_type = current_type
+        if can_match:
+            # We can't narrow the type here, as Mapping key is invariant.
+            new_type = self.type_context[-1]
+            if not o.keys:
+                # Match cannot be refuted, so narrow the remaining type
+                mapping = self.chk.named_type("typing.Mapping")
+                if_type, else_type = self.chk.conditional_types_with_intersection(
+                    current_type,
+                    [TypeRange(mapping, is_upper_bound=False)],
+                    o,
+                    default=current_type,
+                )
+                if not isinstance(current_type, AnyType):
+                    new_type = if_type
+        else:
+            new_type = UninhabitedType()
+        return PatternType(new_type, else_type, captures)
+
+    def get_mapping_item_type(
+        self, pattern: MappingPattern, mapping_type: Type, key: Expression
+    ) -> Type | None:
+        mapping_type = get_proper_type(mapping_type)
+        if isinstance(mapping_type, TypedDictType):
+            with self.msg.filter_errors() as local_errors:
+                result: Type | None = self.chk.expr_checker.visit_typeddict_index_expr(
+                    mapping_type, key
+                )[0]
+                has_local_errors = local_errors.has_new_errors()
+            # If we can't determine the type statically fall back to treating it as a normal
+            # mapping
+            if has_local_errors:
+                with self.msg.filter_errors() as local_errors:
+                    result = self.get_simple_mapping_item_type(pattern, mapping_type, key)
+
+                    if local_errors.has_new_errors():
+                        result = None
+        else:
+            with self.msg.filter_errors():
+                result = self.get_simple_mapping_item_type(pattern, mapping_type, key)
+        return result
+
+    def get_simple_mapping_item_type(
+        self, pattern: MappingPattern, mapping_type: Type, key: Expression
+    ) -> Type:
+        result, _ = self.chk.expr_checker.check_method_call_by_name(
+            "__getitem__", mapping_type, [key], [ARG_POS], pattern
+        )
+        return result
+
+    def visit_class_pattern(self, o: ClassPattern) -> PatternType:
+        current_type = get_proper_type(self.type_context[-1])
+
+        #
+        # Check class type
+        #
+        type_info = o.class_ref.node
+        if isinstance(type_info, TypeAlias) and not type_info.no_args:
+            self.msg.fail(message_registry.CLASS_PATTERN_GENERIC_TYPE_ALIAS, o)
+            return self.early_non_match()
+
+        typ = self.chk.expr_checker.accept(o.class_ref)
+        type_ranges = self.get_class_pattern_type_ranges(typ, o)
+        if type_ranges is None:
+            return self.early_non_match()
+        typ = UnionType.make_union([t.item for t in type_ranges])
+
+        new_type, rest_type = self.chk.conditional_types_with_intersection(
+            current_type, type_ranges, o, default=current_type
+        )
+        if is_uninhabited(new_type):
+            return self.early_non_match()
+        # TODO: Do I need this?
+        narrowed_type = narrow_declared_type(current_type, new_type)
+
+        #
+        # Convert positional to keyword patterns
+        #
+        keyword_pairs: list[tuple[str | None, Pattern]] = []
+        match_arg_set: set[str] = set()
+
+        captures: dict[Expression, Type] = {}
+
+        if len(o.positionals) != 0:
+            if self.should_self_match(typ):
+                if len(o.positionals) > 1:
+                    self.msg.fail(message_registry.CLASS_PATTERN_TOO_MANY_POSITIONAL_ARGS, o)
+                pattern_type = self.accept(o.positionals[0], narrowed_type)
+                if not is_uninhabited(pattern_type.type):
+                    return PatternType(
+                        pattern_type.type,
+                        join_types(rest_type, pattern_type.rest_type),
+                        pattern_type.captures,
+                    )
+                captures = pattern_type.captures
+            else:
+                with self.msg.filter_errors() as local_errors:
+                    match_args_type = analyze_member_access(
+                        "__match_args__",
+                        typ,
+                        o,
+                        is_lvalue=False,
+                        is_super=False,
+                        is_operator=False,
+                        original_type=typ,
+                        chk=self.chk,
+                    )
+                    has_local_errors = local_errors.has_new_errors()
+                if has_local_errors:
+                    self.msg.fail(
+                        message_registry.MISSING_MATCH_ARGS.format(
+                            typ.str_with_options(self.options)
+                        ),
+                        o,
+                    )
+                    return self.early_non_match()
+
+                proper_match_args_type = get_proper_type(match_args_type)
+                if isinstance(proper_match_args_type, TupleType):
+                    match_arg_names = get_match_arg_names(proper_match_args_type)
+
+                    if len(o.positionals) > len(match_arg_names):
+                        self.msg.fail(message_registry.CLASS_PATTERN_TOO_MANY_POSITIONAL_ARGS, o)
+                        return self.early_non_match()
+                else:
+                    match_arg_names = [None] * len(o.positionals)
+
+                for arg_name, pos in zip(match_arg_names, o.positionals):
+                    keyword_pairs.append((arg_name, pos))
+                    if arg_name is not None:
+                        match_arg_set.add(arg_name)
+
+        #
+        # Check for duplicate patterns
+        #
+        keyword_arg_set = set()
+        has_duplicates = False
+        for key, value in zip(o.keyword_keys, o.keyword_values):
+            keyword_pairs.append((key, value))
+            if key in match_arg_set:
+                self.msg.fail(
+                    message_registry.CLASS_PATTERN_KEYWORD_MATCHES_POSITIONAL.format(key), value
+                )
+                has_duplicates = True
+            elif key in keyword_arg_set:
+                self.msg.fail(
+                    message_registry.CLASS_PATTERN_DUPLICATE_KEYWORD_PATTERN.format(key), value
+                )
+                has_duplicates = True
+            keyword_arg_set.add(key)
+
+        if has_duplicates:
+            return self.early_non_match()
+
+        #
+        # Check keyword patterns
+        #
+        can_match = True
+        for keyword, pattern in keyword_pairs:
+            key_type: Type | None = None
+            with self.msg.filter_errors() as local_errors:
+                if keyword is not None:
+                    key_type = analyze_member_access(
+                        keyword,
+                        narrowed_type,
+                        pattern,
+                        is_lvalue=False,
+                        is_super=False,
+                        is_operator=False,
+                        original_type=new_type,
+                        chk=self.chk,
+                    )
+                else:
+                    key_type = AnyType(TypeOfAny.from_error)
+                has_local_errors = local_errors.has_new_errors()
+            if has_local_errors or key_type is None:
+                key_type = AnyType(TypeOfAny.from_error)
+                if not (type_info and type_info.fullname == "builtins.object"):
+                    self.msg.fail(
+                        message_registry.CLASS_PATTERN_UNKNOWN_KEYWORD.format(
+                            typ.str_with_options(self.options), keyword
+                        ),
+                        pattern,
+                    )
+                elif keyword is not None:
+                    new_type = self.chk.add_any_attribute_to_type(new_type, keyword)
+
+            inner_type, inner_rest_type, inner_captures = self.accept(pattern, key_type)
+            if is_uninhabited(inner_type):
+                can_match = False
+            else:
+                self.update_type_map(captures, inner_captures)
+                if not is_uninhabited(inner_rest_type):
+                    rest_type = current_type
+
+        if not can_match:
+            new_type = UninhabitedType()
+        return PatternType(new_type, rest_type, captures)
+
+    def get_class_pattern_type_ranges(self, typ: Type, o: ClassPattern) -> list[TypeRange] | None:
+        p_typ = get_proper_type(typ)
+
+        if isinstance(p_typ, UnionType):
+            type_ranges = []
+            for item in p_typ.items:
+                type_range = self.get_class_pattern_type_ranges(item, o)
+                if type_range is not None:
+                    type_ranges.extend(type_range)
+            if not type_ranges:
+                return None
+            return type_ranges
+
+        if isinstance(p_typ, FunctionLike) and p_typ.is_type_obj():
+            typ = fill_typevars_with_any(p_typ.type_object())
+            return [TypeRange(typ, is_upper_bound=False)]
+        if (
+            isinstance(o.class_ref.node, Var)
+            and o.class_ref.node.type is not None
+            and o.class_ref.node.fullname == "typing.Callable"
+        ):
+            # Create a `Callable[..., Any]`
+            fallback = self.chk.named_type("builtins.function")
+            any_type = AnyType(TypeOfAny.unannotated)
+            typ = callable_with_ellipsis(any_type, ret_type=any_type, fallback=fallback)
+            return [TypeRange(typ, is_upper_bound=False)]
+        if isinstance(p_typ, TypeType):
+            typ = p_typ.item
+            return [TypeRange(p_typ.item, is_upper_bound=True)]
+        if isinstance(p_typ, AnyType):
+            return [TypeRange(p_typ, is_upper_bound=False)]
+
+        self.msg.fail(
+            message_registry.CLASS_PATTERN_TYPE_REQUIRED.format(
+                typ.str_with_options(self.options)
+            ),
+            o,
+        )
+        return None
+
+    def should_self_match(self, typ: Type) -> bool:
+        typ = get_proper_type(typ)
+        if isinstance(typ, TupleType):
+            typ = typ.partial_fallback
+        if isinstance(typ, AnyType):
+            return False
+        if isinstance(typ, Instance) and typ.type.get("__match_args__") is not None:
+            # Named tuples and other subtypes of builtins that define __match_args__
+            # should not self match.
+            return False
+        for other in self.self_match_types:
+            if is_subtype(typ, other):
+                return True
+        return False
+
+    def can_match_sequence(self, typ: ProperType) -> bool:
+        if isinstance(typ, AnyType):
+            return True
+        if isinstance(typ, UnionType):
+            return any(self.can_match_sequence(get_proper_type(item)) for item in typ.items)
+        for other in self.non_sequence_match_types:
+            # We have to ignore promotions, as memoryview should match, but bytes,
+            # which it can be promoted to, shouldn't
+            if is_subtype(typ, other, ignore_promotions=True):
+                return False
+        sequence = self.chk.named_type("typing.Sequence")
+        # If the static type is more general than sequence the actual type could still match
+        return is_subtype(typ, sequence) or is_subtype(sequence, typ)
+
+    def generate_types_from_names(self, type_names: list[str]) -> list[Type]:
+        types: list[Type] = []
+        for name in type_names:
+            try:
+                types.append(self.chk.named_type(name))
+            except KeyError as e:
+                # Some built in types are not defined in all test cases
+                if not name.startswith("builtins."):
+                    raise e
+        return types
+
+    def update_type_map(
+        self, original_type_map: dict[Expression, Type], extra_type_map: dict[Expression, Type]
+    ) -> None:
+        # Calculating this would not be needed if TypeMap directly used literal hashes instead of
+        # expressions, as suggested in the TODO above it's definition
+        already_captured = {literal_hash(expr) for expr in original_type_map}
+        for expr, typ in extra_type_map.items():
+            if literal_hash(expr) in already_captured:
+                node = get_var(expr)
+                self.msg.fail(
+                    message_registry.MULTIPLE_ASSIGNMENTS_IN_PATTERN.format(node.name), expr
+                )
+            else:
+                original_type_map[expr] = typ
+
+    def construct_sequence_child(self, outer_type: Type, inner_type: Type) -> Type:
+        """
+        If outer_type is a child class of typing.Sequence returns a new instance of
+        outer_type, that is a Sequence of inner_type. If outer_type is not a child class of
+        typing.Sequence just returns a Sequence of inner_type
+
+        For example:
+        construct_sequence_child(List[int], str) = List[str]
+
+        TODO: this doesn't make sense. For example if one has class S(Sequence[int], Generic[T])
+        or class T(Sequence[Tuple[T, T]]), there is no way any of those can map to Sequence[str].
+        """
+        proper_type = get_proper_type(outer_type)
+        if isinstance(proper_type, TypeVarType):
+            new_bound = self.construct_sequence_child(proper_type.upper_bound, inner_type)
+            return proper_type.copy_modified(upper_bound=new_bound)
+        if isinstance(proper_type, AnyType):
+            return outer_type
+        if isinstance(proper_type, UnionType):
+            types = [
+                self.construct_sequence_child(item, inner_type)
+                for item in proper_type.items
+                if self.can_match_sequence(get_proper_type(item))
+            ]
+            return make_simplified_union(types)
+        sequence = self.chk.named_generic_type("typing.Sequence", [inner_type])
+        if is_subtype(outer_type, self.chk.named_type("typing.Sequence")):
+            if isinstance(proper_type, TupleType):
+                proper_type = tuple_fallback(proper_type)
+            assert isinstance(proper_type, Instance)
+            empty_type = fill_typevars(proper_type.type)
+            partial_type = expand_type_by_instance(empty_type, sequence)
+            return expand_type_by_instance(partial_type, proper_type)
+        else:
+            return sequence
+
+    def early_non_match(self) -> PatternType:
+        return PatternType(UninhabitedType(), self.type_context[-1], {})
+
+
+def get_match_arg_names(typ: TupleType) -> list[str | None]:
+    args: list[str | None] = []
+    for item in typ.items:
+        values = try_getting_str_literals_from_type(item)
+        if values is None or len(values) != 1:
+            args.append(None)
+        else:
+            args.append(values[0])
+    return args
+
+
+def get_var(expr: Expression) -> Var:
+    """
+    Warning: this in only true for expressions captured by a match statement.
+    Don't call it from anywhere else
+    """
+    assert isinstance(expr, NameExpr), expr
+    node = expr.node
+    assert isinstance(node, Var), node
+    return node
+
+
+def get_type_range(typ: Type) -> TypeRange:
+    typ = get_proper_type(typ)
+    if (
+        isinstance(typ, Instance)
+        and typ.last_known_value
+        and isinstance(typ.last_known_value.value, bool)
+    ):
+        typ = typ.last_known_value
+    return TypeRange(typ, is_upper_bound=False)
+
+
+def is_uninhabited(typ: Type) -> bool:
+    return isinstance(get_proper_type(typ), UninhabitedType)

venv/lib/python3.11/site-packages/mypy/config_parser.py

@@ -0,0 +1,734 @@
+from __future__ import annotations
+
+import argparse
+import configparser
+import glob as fileglob
+import os
+import re
+import sys
+from io import StringIO
+
+if sys.version_info >= (3, 11):
+    import tomllib
+else:
+    import tomli as tomllib
+
+from collections.abc import Callable, Mapping, MutableMapping, Sequence
+from typing import Any, Final, TextIO, TypeAlias
+from typing_extensions import Never
+
+from mypy import defaults
+from mypy.options import PER_MODULE_OPTIONS, Options
+
+_CONFIG_VALUE_TYPES: TypeAlias = (
+    str | bool | int | float | dict[str, str] | list[str] | tuple[int, int]
+)
+_INI_PARSER_CALLABLE: TypeAlias = Callable[[Any], _CONFIG_VALUE_TYPES]
+
+
+class VersionTypeError(argparse.ArgumentTypeError):
+    """Provide a fallback value if the Python version is unsupported."""
+
+    def __init__(self, *args: Any, fallback: tuple[int, int]) -> None:
+        self.fallback = fallback
+        super().__init__(*args)
+
+
+def parse_version(v: str | float) -> tuple[int, int]:
+    m = re.match(r"\A(\d)\.(\d+)\Z", str(v))
+    if not m:
+        raise argparse.ArgumentTypeError(f"Invalid python version '{v}' (expected format: 'x.y')")
+    major, minor = int(m.group(1)), int(m.group(2))
+    if major == 2 and minor == 7:
+        pass  # Error raised elsewhere
+    elif major == 3:
+        if minor < defaults.PYTHON3_VERSION_MIN[1]:
+            msg = "Python 3.{} is not supported (must be {}.{} or higher)".format(
+                minor, *defaults.PYTHON3_VERSION_MIN
+            )
+
+            if isinstance(v, float):
+                msg += ". You may need to put quotes around your Python version"
+
+            raise VersionTypeError(msg, fallback=defaults.PYTHON3_VERSION_MIN)
+    else:
+        raise argparse.ArgumentTypeError(
+            f"Python major version '{major}' out of range (must be 3)"
+        )
+    return major, minor
+
+
+def try_split(v: str | Sequence[str] | object, split_regex: str = ",") -> list[str]:
+    """Split and trim a str or sequence (eg: list) of str into a list of str.
+    If an element of the input is not str, a type error will be raised."""
+
+    def complain(x: object, additional_info: str = "") -> Never:
+        raise argparse.ArgumentTypeError(
+            f"Expected a list or a stringified version thereof, but got: '{x}', of type {type(x).__name__}.{additional_info}"
+        )
+
+    if isinstance(v, str):
+        items = [p.strip() for p in re.split(split_regex, v)]
+        if items and items[-1] == "":
+            items.pop(-1)
+        return items
+    elif isinstance(v, Sequence):
+        return [
+            (
+                p.strip()
+                if isinstance(p, str)
+                else complain(p, additional_info=" (As an element of the list.)")
+            )
+            for p in v
+        ]
+    else:
+        complain(v)
+
+
+def validate_package_allow_list(allow_list: list[str]) -> list[str]:
+    for p in allow_list:
+        msg = f"Invalid allow list entry: {p}"
+        if "*" in p:
+            raise argparse.ArgumentTypeError(
+                f"{msg} (entries are already prefixes so must not contain *)"
+            )
+        if "\\" in p or "/" in p:
+            raise argparse.ArgumentTypeError(
+                f"{msg} (entries must be packages like foo.bar not directories or files)"
+            )
+    return allow_list
+
+
+def expand_path(path: str) -> str:
+    """Expand the user home directory and any environment variables contained within
+    the provided path.
+    """
+
+    return os.path.expandvars(os.path.expanduser(path))
+
+
+def str_or_array_as_list(v: str | Sequence[str]) -> list[str]:
+    if isinstance(v, str):
+        return [v.strip()] if v.strip() else []
+    return [p.strip() for p in v if p.strip()]
+
+
+def split_and_match_files_list(paths: Sequence[str]) -> list[str]:
+    """Take a list of files/directories (with support for globbing through the glob library).
+
+    Where a path/glob matches no file, we still include the raw path in the resulting list.
+
+    Returns a list of file paths
+    """
+    expanded_paths = []
+
+    for path in paths:
+        path = expand_path(path.strip())
+        globbed_files = fileglob.glob(path, recursive=True)
+        if globbed_files:
+            expanded_paths.extend(globbed_files)
+        else:
+            expanded_paths.append(path)
+
+    return expanded_paths
+
+
+def split_and_match_files(paths: str) -> list[str]:
+    """Take a string representing a list of files/directories (with support for globbing
+    through the glob library).
+
+    Where a path/glob matches no file, we still include the raw path in the resulting list.
+
+    Returns a list of file paths
+    """
+
+    return split_and_match_files_list(split_commas(paths))
+
+
+def check_follow_imports(choice: str) -> str:
+    choices = ["normal", "silent", "skip", "error"]
+    if choice not in choices:
+        raise argparse.ArgumentTypeError(
+            "invalid choice '{}' (choose from {})".format(
+                choice, ", ".join(f"'{x}'" for x in choices)
+            )
+        )
+    return choice
+
+
+def check_junit_format(choice: str) -> str:
+    choices = ["global", "per_file"]
+    if choice not in choices:
+        raise argparse.ArgumentTypeError(
+            "invalid choice '{}' (choose from {})".format(
+                choice, ", ".join(f"'{x}'" for x in choices)
+            )
+        )
+    return choice
+
+
+def split_commas(value: str) -> list[str]:
+    # Uses a bit smarter technique to allow last trailing comma
+    # and to remove last `""` item from the split.
+    items = value.split(",")
+    if items and items[-1] == "":
+        items.pop(-1)
+    return items
+
+
+# For most options, the type of the default value set in options.py is
+# sufficient, and we don't have to do anything here.  This table
+# exists to specify types for values initialized to None or container
+# types.
+ini_config_types: Final[dict[str, _INI_PARSER_CALLABLE]] = {
+    "python_version": parse_version,
+    "custom_typing_module": str,
+    "custom_typeshed_dir": expand_path,
+    "mypy_path": lambda s: [expand_path(p.strip()) for p in re.split("[,:]", s)],
+    "files": split_and_match_files,
+    "quickstart_file": expand_path,
+    "junit_xml": expand_path,
+    "junit_format": check_junit_format,
+    "follow_imports": check_follow_imports,
+    "no_site_packages": bool,
+    "plugins": lambda s: [p.strip() for p in split_commas(s)],
+    "always_true": lambda s: [p.strip() for p in split_commas(s)],
+    "always_false": lambda s: [p.strip() for p in split_commas(s)],
+    "untyped_calls_exclude": lambda s: validate_package_allow_list(
+        [p.strip() for p in split_commas(s)]
+    ),
+    "enable_incomplete_feature": lambda s: [p.strip() for p in split_commas(s)],
+    "disable_error_code": lambda s: [p.strip() for p in split_commas(s)],
+    "enable_error_code": lambda s: [p.strip() for p in split_commas(s)],
+    "package_root": lambda s: [p.strip() for p in split_commas(s)],
+    "cache_dir": expand_path,
+    "python_executable": expand_path,
+    "strict": bool,
+    "exclude": lambda s: [s.strip()],
+    "packages": try_split,
+    "modules": try_split,
+}
+
+# Reuse the ini_config_types and overwrite the diff
+toml_config_types: Final[dict[str, _INI_PARSER_CALLABLE]] = ini_config_types.copy()
+toml_config_types.update(
+    {
+        "python_version": parse_version,
+        "mypy_path": lambda s: [expand_path(p) for p in try_split(s, "[,:]")],
+        "files": lambda s: split_and_match_files_list(try_split(s)),
+        "junit_format": lambda s: check_junit_format(str(s)),
+        "follow_imports": lambda s: check_follow_imports(str(s)),
+        "plugins": try_split,
+        "always_true": try_split,
+        "always_false": try_split,
+        "untyped_calls_exclude": lambda s: validate_package_allow_list(try_split(s)),
+        "enable_incomplete_feature": try_split,
+        "disable_error_code": lambda s: try_split(s),
+        "enable_error_code": lambda s: try_split(s),
+        "package_root": try_split,
+        "exclude": str_or_array_as_list,
+        "packages": try_split,
+        "modules": try_split,
+    }
+)
+
+
+def _parse_individual_file(
+    config_file: str, stderr: TextIO | None = None
+) -> tuple[MutableMapping[str, Any], dict[str, _INI_PARSER_CALLABLE], str] | None:
+
+    if not os.path.exists(config_file):
+        return None
+
+    parser: MutableMapping[str, Any]
+    try:
+        if is_toml(config_file):
+            with open(config_file, "rb") as f:
+                toml_data = tomllib.load(f)
+            # Filter down to just mypy relevant toml keys
+            toml_data = toml_data.get("tool", {})
+            if "mypy" not in toml_data:
+                return None
+            toml_data = {"mypy": toml_data["mypy"]}
+            parser = destructure_overrides(toml_data)
+            config_types = toml_config_types
+        else:
+            parser = configparser.RawConfigParser()
+            parser.read(config_file)
+            config_types = ini_config_types
+
+    except (tomllib.TOMLDecodeError, configparser.Error, ConfigTOMLValueError) as err:
+        print(f"{config_file}: {err}", file=stderr)
+        return None
+
+    if os.path.basename(config_file) in defaults.SHARED_CONFIG_NAMES and "mypy" not in parser:
+        return None
+
+    return parser, config_types, config_file
+
+
+def _find_config_file(
+    stderr: TextIO | None = None,
+) -> tuple[MutableMapping[str, Any], dict[str, _INI_PARSER_CALLABLE], str] | None:
+
+    current_dir = os.path.abspath(os.getcwd())
+
+    while True:
+        for name in defaults.CONFIG_NAMES + defaults.SHARED_CONFIG_NAMES:
+            config_file = os.path.relpath(os.path.join(current_dir, name))
+            ret = _parse_individual_file(config_file, stderr)
+            if ret is None:
+                continue
+            return ret
+
+        if any(
+            os.path.exists(os.path.join(current_dir, cvs_root)) for cvs_root in (".git", ".hg")
+        ):
+            break
+        parent_dir = os.path.dirname(current_dir)
+        if parent_dir == current_dir:
+            break
+        current_dir = parent_dir
+
+    for config_file in defaults.USER_CONFIG_FILES:
+        ret = _parse_individual_file(config_file, stderr)
+        if ret is None:
+            continue
+        return ret
+
+    return None
+
+
+def parse_config_file(
+    options: Options,
+    set_strict_flags: Callable[[], None],
+    filename: str | None,
+    stdout: TextIO | None = None,
+    stderr: TextIO | None = None,
+) -> None:
+    """Parse a config file into an Options object.
+
+    Errors are written to stderr but are not fatal.
+
+    If filename is None, fall back to default config files.
+    """
+    stdout = stdout or sys.stdout
+    stderr = stderr or sys.stderr
+
+    ret = (
+        _parse_individual_file(filename, stderr)
+        if filename is not None
+        else _find_config_file(stderr)
+    )
+    if ret is None:
+        return
+    parser, config_types, file_read = ret
+
+    options.config_file = file_read
+    os.environ["MYPY_CONFIG_FILE_DIR"] = os.path.dirname(os.path.abspath(file_read))
+
+    if "mypy" not in parser:
+        if filename or os.path.basename(file_read) not in defaults.SHARED_CONFIG_NAMES:
+            print(f"{file_read}: No [mypy] section in config file", file=stderr)
+    else:
+        section = parser["mypy"]
+        prefix = f"{file_read}: [mypy]: "
+        updates, report_dirs = parse_section(
+            prefix, options, set_strict_flags, section, config_types, stderr
+        )
+        for k, v in updates.items():
+            setattr(options, k, v)
+        options.report_dirs.update(report_dirs)
+
+    for name, section in parser.items():
+        if name.startswith("mypy-"):
+            prefix = get_prefix(file_read, name)
+            updates, report_dirs = parse_section(
+                prefix, options, set_strict_flags, section, config_types, stderr
+            )
+            if report_dirs:
+                print(
+                    prefix,
+                    "Per-module sections should not specify reports ({})".format(
+                        ", ".join(s + "_report" for s in sorted(report_dirs))
+                    ),
+                    file=stderr,
+                )
+            if set(updates) - PER_MODULE_OPTIONS:
+                print(
+                    prefix,
+                    "Per-module sections should only specify per-module flags ({})".format(
+                        ", ".join(sorted(set(updates) - PER_MODULE_OPTIONS))
+                    ),
+                    file=stderr,
+                )
+                updates = {k: v for k, v in updates.items() if k in PER_MODULE_OPTIONS}
+
+            globs = name[5:]
+            for glob in globs.split(","):
+                # For backwards compatibility, replace (back)slashes with dots.
+                glob = glob.replace(os.sep, ".")
+                if os.altsep:
+                    glob = glob.replace(os.altsep, ".")
+
+                if any(c in glob for c in "?[]!") or any(
+                    "*" in x and x != "*" for x in glob.split(".")
+                ):
+                    print(
+                        prefix,
+                        "Patterns must be fully-qualified module names, optionally "
+                        "with '*' in some components (e.g spam.*.eggs.*)",
+                        file=stderr,
+                    )
+                else:
+                    options.per_module_options[glob] = updates
+
+
+def get_prefix(file_read: str, name: str) -> str:
+    if is_toml(file_read):
+        module_name_str = 'module = "%s"' % "-".join(name.split("-")[1:])
+    else:
+        module_name_str = name
+
+    return f"{file_read}: [{module_name_str}]:"
+
+
+def is_toml(filename: str) -> bool:
+    return filename.lower().endswith(".toml")
+
+
+def destructure_overrides(toml_data: dict[str, Any]) -> dict[str, Any]:
+    """Take the new [[tool.mypy.overrides]] section array in the pyproject.toml file,
+    and convert it back to a flatter structure that the existing config_parser can handle.
+
+    E.g. the following pyproject.toml file:
+
+        [[tool.mypy.overrides]]
+        module = [
+            "a.b",
+            "b.*"
+        ]
+        disallow_untyped_defs = true
+
+        [[tool.mypy.overrides]]
+        module = 'c'
+        disallow_untyped_defs = false
+
+    Would map to the following config dict that it would have gotten from parsing an equivalent
+    ini file:
+
+        {
+            "mypy-a.b": {
+                disallow_untyped_defs = true,
+            },
+            "mypy-b.*": {
+                disallow_untyped_defs = true,
+            },
+            "mypy-c": {
+                disallow_untyped_defs: false,
+            },
+        }
+    """
+    if "overrides" not in toml_data["mypy"]:
+        return toml_data
+
+    if not isinstance(toml_data["mypy"]["overrides"], list):
+        raise ConfigTOMLValueError(
+            "tool.mypy.overrides sections must be an array. Please make "
+            "sure you are using double brackets like so: [[tool.mypy.overrides]]"
+        )
+
+    result = toml_data.copy()
+    for override in result["mypy"]["overrides"]:
+        if "module" not in override:
+            raise ConfigTOMLValueError(
+                "toml config file contains a [[tool.mypy.overrides]] "
+                "section, but no module to override was specified."
+            )
+
+        if isinstance(override["module"], str):
+            modules = [override["module"]]
+        elif isinstance(override["module"], list):
+            modules = override["module"]
+        else:
+            raise ConfigTOMLValueError(
+                "toml config file contains a [[tool.mypy.overrides]] "
+                "section with a module value that is not a string or a list of "
+                "strings"
+            )
+
+        for module in modules:
+            module_overrides = override.copy()
+            del module_overrides["module"]
+            old_config_name = f"mypy-{module}"
+            if old_config_name not in result:
+                result[old_config_name] = module_overrides
+            else:
+                for new_key, new_value in module_overrides.items():
+                    if (
+                        new_key in result[old_config_name]
+                        and result[old_config_name][new_key] != new_value
+                    ):
+                        raise ConfigTOMLValueError(
+                            "toml config file contains "
+                            "[[tool.mypy.overrides]] sections with conflicting "
+                            f"values. Module '{module}' has two different values for '{new_key}'"
+                        )
+                    result[old_config_name][new_key] = new_value
+
+    del result["mypy"]["overrides"]
+    return result
+
+
+def parse_section(
+    prefix: str,
+    template: Options,
+    set_strict_flags: Callable[[], None],
+    section: Mapping[str, Any],
+    config_types: dict[str, Any],
+    stderr: TextIO = sys.stderr,
+) -> tuple[dict[str, object], dict[str, str]]:
+    """Parse one section of a config file.
+
+    Returns a dict of option values encountered, and a dict of report directories.
+    """
+    results: dict[str, object] = {}
+    report_dirs: dict[str, str] = {}
+
+    # Because these fields exist on Options, without proactive checking, we would accept them
+    # and crash later
+    invalid_options = {
+        "enabled_error_codes": "enable_error_code",
+        "disabled_error_codes": "disable_error_code",
+    }
+
+    for key in section:
+        invert = False
+        # Here we use `key` for original config section key, and `options_key` for
+        # the corresponding Options attribute.
+        options_key = key
+        # Match aliasing for command line flag.
+        if key.endswith("allow_redefinition"):
+            options_key += "_old"
+        if key in config_types:
+            ct = config_types[key]
+        elif key in invalid_options:
+            print(
+                f"{prefix}Unrecognized option: {key} = {section[key]}"
+                f" (did you mean {invalid_options[key]}?)",
+                file=stderr,
+            )
+            continue
+        else:
+            dv = getattr(template, options_key, None)
+            if dv is None:
+                if key.endswith("_report"):
+                    report_type = key[:-7].replace("_", "-")
+                    if report_type in defaults.REPORTER_NAMES:
+                        report_dirs[report_type] = str(section[key])
+                    else:
+                        print(f"{prefix}Unrecognized report type: {key}", file=stderr)
+                    continue
+                if key.startswith("x_"):
+                    pass  # Don't complain about `x_blah` flags
+                elif key.startswith("no_") and hasattr(template, options_key[3:]):
+                    options_key = options_key[3:]
+                    invert = True
+                elif key.startswith("allow") and hasattr(template, "dis" + options_key):
+                    options_key = "dis" + options_key
+                    invert = True
+                elif key.startswith("disallow") and hasattr(template, options_key[3:]):
+                    options_key = options_key[3:]
+                    invert = True
+                elif key.startswith("show_") and hasattr(template, "hide_" + options_key[5:]):
+                    options_key = "hide_" + options_key[5:]
+                    invert = True
+                elif key == "strict":
+                    pass  # Special handling below
+                else:
+                    print(f"{prefix}Unrecognized option: {key} = {section[key]}", file=stderr)
+                if invert:
+                    dv = getattr(template, options_key, None)
+                else:
+                    continue
+            ct = type(dv) if dv is not None else None
+        v: Any = None
+        try:
+            if ct is bool:
+                if isinstance(section, dict):
+                    v = convert_to_boolean(section.get(key))
+                else:
+                    v = section.getboolean(key)  # type: ignore[attr-defined]  # Until better stub
+                if invert:
+                    v = not v
+            elif callable(ct):
+                if invert:
+                    print(f"{prefix}Can not invert non-boolean key {options_key}", file=stderr)
+                    continue
+                try:
+                    v = ct(section.get(key))
+                except VersionTypeError as err_version:
+                    print(f"{prefix}{key}: {err_version}", file=stderr)
+                    v = err_version.fallback
+                except argparse.ArgumentTypeError as err:
+                    print(f"{prefix}{key}: {err}", file=stderr)
+                    continue
+            else:
+                print(f"{prefix}Don't know what type {key} should have", file=stderr)
+                continue
+        except ValueError as err:
+            print(f"{prefix}{key}: {err}", file=stderr)
+            continue
+        if key == "strict":
+            if v:
+                set_strict_flags()
+            continue
+        results[options_key] = v
+
+    # These two flags act as per-module overrides, so store the empty defaults.
+    if "disable_error_code" not in results:
+        results["disable_error_code"] = []
+    if "enable_error_code" not in results:
+        results["enable_error_code"] = []
+
+    return results, report_dirs
+
+
+def convert_to_boolean(value: Any | None) -> bool:
+    """Return a boolean value translating from other types if necessary."""
+    if isinstance(value, bool):
+        return value
+    if not isinstance(value, str):
+        value = str(value)
+    if value.lower() not in configparser.RawConfigParser.BOOLEAN_STATES:
+        raise ValueError(f"Not a boolean: {value}")
+    return configparser.RawConfigParser.BOOLEAN_STATES[value.lower()]
+
+
+def split_directive(s: str) -> tuple[list[str], list[str]]:
+    """Split s on commas, except during quoted sections.
+
+    Returns the parts and a list of error messages."""
+    parts = []
+    cur: list[str] = []
+    errors = []
+    i = 0
+    while i < len(s):
+        if s[i] == ",":
+            parts.append("".join(cur).strip())
+            cur = []
+        elif s[i] == '"':
+            i += 1
+            while i < len(s) and s[i] != '"':
+                cur.append(s[i])
+                i += 1
+            if i == len(s):
+                errors.append("Unterminated quote in configuration comment")
+                cur.clear()
+        else:
+            cur.append(s[i])
+        i += 1
+    if cur:
+        parts.append("".join(cur).strip())
+
+    return parts, errors
+
+
+def mypy_comments_to_config_map(line: str, template: Options) -> tuple[dict[str, str], list[str]]:
+    """Rewrite the mypy comment syntax into ini file syntax."""
+    options = {}
+    entries, errors = split_directive(line)
+    for entry in entries:
+        if "=" not in entry:
+            name = entry
+            value = None
+        else:
+            name, value = (x.strip() for x in entry.split("=", 1))
+
+        name = name.replace("-", "_")
+        if value is None:
+            value = "True"
+        options[name] = value
+
+    return options, errors
+
+
+def parse_mypy_comments(
+    args: list[tuple[int, str]], template: Options
+) -> tuple[dict[str, object], list[tuple[int, str]]]:
+    """Parse a collection of inline mypy: configuration comments.
+
+    Returns a dictionary of options to be applied and a list of error messages
+    generated.
+    """
+    errors: list[tuple[int, str]] = []
+    sections: dict[str, object] = {"enable_error_code": [], "disable_error_code": []}
+
+    for lineno, line in args:
+        # In order to easily match the behavior for bools, we abuse configparser.
+        # Oddly, the only way to get the SectionProxy object with the getboolean
+        # method is to create a config parser.
+        parser = configparser.RawConfigParser()
+        options, parse_errors = mypy_comments_to_config_map(line, template)
+        if "python_version" in options:
+            errors.append((lineno, "python_version not supported in inline configuration"))
+            del options["python_version"]
+
+        parser["dummy"] = options
+        errors.extend((lineno, x) for x in parse_errors)
+
+        stderr = StringIO()
+        strict_found = False
+
+        def set_strict_flags() -> None:
+            nonlocal strict_found
+            strict_found = True
+
+        new_sections, reports = parse_section(
+            "", template, set_strict_flags, parser["dummy"], ini_config_types, stderr=stderr
+        )
+        errors.extend((lineno, x) for x in stderr.getvalue().strip().split("\n") if x)
+        if reports:
+            errors.append((lineno, "Reports not supported in inline configuration"))
+        if strict_found:
+            errors.append(
+                (
+                    lineno,
+                    'Setting "strict" not supported in inline configuration: specify it in '
+                    "a configuration file instead, or set individual inline flags "
+                    '(see "mypy -h" for the list of flags enabled in strict mode)',
+                )
+            )
+        # Because this is currently special-cased
+        # (the new_sections for an inline config *always* includes 'disable_error_code' and
+        # 'enable_error_code' fields, usually empty, which overwrite the old ones),
+        # we have to manipulate them specially.
+        # This could use a refactor, but so could the whole subsystem.
+        if (
+            "enable_error_code" in new_sections
+            and isinstance(neec := new_sections["enable_error_code"], list)
+            and isinstance(eec := sections.get("enable_error_code", []), list)
+        ):
+            new_sections["enable_error_code"] = sorted(set(neec + eec))
+        if (
+            "disable_error_code" in new_sections
+            and isinstance(ndec := new_sections["disable_error_code"], list)
+            and isinstance(dec := sections.get("disable_error_code", []), list)
+        ):
+            new_sections["disable_error_code"] = sorted(set(ndec + dec))
+        sections.update(new_sections)
+    return sections, errors
+
+
+def get_config_module_names(filename: str | None, modules: list[str]) -> str:
+    if not filename or not modules:
+        return ""
+
+    if not is_toml(filename):
+        return ", ".join(f"[mypy-{module}]" for module in modules)
+
+    return "module = ['%s']" % ("', '".join(sorted(modules)))
+
+
+class ConfigTOMLValueError(ValueError):
+    pass

venv/lib/python3.11/site-packages/mypy/constant_fold.py

@@ -0,0 +1,187 @@
+"""Constant folding of expressions.
+
+For example, 3 + 5 can be constant folded into 8.
+"""
+
+from __future__ import annotations
+
+from typing import Final
+
+from mypy.nodes import (
+    ComplexExpr,
+    Expression,
+    FloatExpr,
+    IntExpr,
+    NameExpr,
+    OpExpr,
+    StrExpr,
+    UnaryExpr,
+    Var,
+)
+
+# All possible result types of constant folding
+ConstantValue = int | bool | float | complex | str
+CONST_TYPES: Final = (int, bool, float, complex, str)
+
+
+def constant_fold_expr(expr: Expression, cur_mod_id: str) -> ConstantValue | None:
+    """Return the constant value of an expression for supported operations.
+
+    Among other things, support int arithmetic and string
+    concatenation. For example, the expression 3 + 5 has the constant
+    value 8.
+
+    Also bind simple references to final constants defined in the
+    current module (cur_mod_id). Binding to references is best effort
+    -- we don't bind references to other modules. Mypyc trusts these
+    to be correct in compiled modules, so that it can replace a
+    constant expression (or a reference to one) with the statically
+    computed value. We don't want to infer constant values based on
+    stubs, in particular, as these might not match the implementation
+    (due to version skew, for example).
+
+    Return None if unsuccessful.
+    """
+    if isinstance(expr, IntExpr):
+        return expr.value
+    if isinstance(expr, StrExpr):
+        return expr.value
+    if isinstance(expr, FloatExpr):
+        return expr.value
+    if isinstance(expr, ComplexExpr):
+        return expr.value
+    elif isinstance(expr, NameExpr):
+        if expr.name == "True":
+            return True
+        elif expr.name == "False":
+            return False
+        node = expr.node
+        if (
+            isinstance(node, Var)
+            and node.is_final
+            and node.fullname.rsplit(".", 1)[0] == cur_mod_id
+        ):
+            value = node.final_value
+            if isinstance(value, (CONST_TYPES)):
+                return value
+    elif isinstance(expr, OpExpr):
+        left = constant_fold_expr(expr.left, cur_mod_id)
+        right = constant_fold_expr(expr.right, cur_mod_id)
+        if left is not None and right is not None:
+            return constant_fold_binary_op(expr.op, left, right)
+    elif isinstance(expr, UnaryExpr):
+        value = constant_fold_expr(expr.expr, cur_mod_id)
+        if value is not None:
+            return constant_fold_unary_op(expr.op, value)
+    return None
+
+
+def constant_fold_binary_op(
+    op: str, left: ConstantValue, right: ConstantValue
+) -> ConstantValue | None:
+    if isinstance(left, int) and isinstance(right, int):
+        return constant_fold_binary_int_op(op, left, right)
+
+    # Float and mixed int/float arithmetic.
+    if isinstance(left, float) and isinstance(right, float):
+        return constant_fold_binary_float_op(op, left, right)
+    elif isinstance(left, float) and isinstance(right, int):
+        return constant_fold_binary_float_op(op, left, right)
+    elif isinstance(left, int) and isinstance(right, float):
+        return constant_fold_binary_float_op(op, left, right)
+
+    # String concatenation and multiplication.
+    if op == "+" and isinstance(left, str) and isinstance(right, str):
+        return left + right
+    elif op == "*" and isinstance(left, str) and isinstance(right, int):
+        return left * right
+    elif op == "*" and isinstance(left, int) and isinstance(right, str):
+        return left * right
+
+    # Complex construction.
+    if op == "+" and isinstance(left, (int, float)) and isinstance(right, complex):
+        return left + right
+    elif op == "+" and isinstance(left, complex) and isinstance(right, (int, float)):
+        return left + right
+    elif op == "-" and isinstance(left, (int, float)) and isinstance(right, complex):
+        return left - right
+    elif op == "-" and isinstance(left, complex) and isinstance(right, (int, float)):
+        return left - right
+
+    return None
+
+
+def constant_fold_binary_int_op(op: str, left: int, right: int) -> int | float | None:
+    if op == "+":
+        return left + right
+    if op == "-":
+        return left - right
+    elif op == "*":
+        return left * right
+    elif op == "/":
+        if right != 0:
+            return left / right
+    elif op == "//":
+        if right != 0:
+            return left // right
+    elif op == "%":
+        if right != 0:
+            return left % right
+    elif op == "&":
+        return left & right
+    elif op == "|":
+        return left | right
+    elif op == "^":
+        return left ^ right
+    elif op == "<<":
+        if right >= 0:
+            return left << right
+    elif op == ">>":
+        if right >= 0:
+            return left >> right
+    elif op == "**":
+        if right >= 0:
+            ret = left**right
+            assert isinstance(ret, int)
+            return ret
+    return None
+
+
+def constant_fold_binary_float_op(op: str, left: int | float, right: int | float) -> float | None:
+    assert not (isinstance(left, int) and isinstance(right, int)), (op, left, right)
+    if op == "+":
+        return left + right
+    elif op == "-":
+        return left - right
+    elif op == "*":
+        return left * right
+    elif op == "/":
+        if right != 0:
+            return left / right
+    elif op == "//":
+        if right != 0:
+            return left // right
+    elif op == "%":
+        if right != 0:
+            return left % right
+    elif op == "**":
+        if (left < 0 and isinstance(right, int)) or left > 0:
+            try:
+                ret = left**right
+            except OverflowError:
+                return None
+            else:
+                assert isinstance(ret, float), ret
+                return ret
+
+    return None
+
+
+def constant_fold_unary_op(op: str, value: ConstantValue) -> int | float | None:
+    if op == "-" and isinstance(value, (int, float)):
+        return -value
+    elif op == "~" and isinstance(value, int):
+        return ~value
+    elif op == "+" and isinstance(value, (int, float)):
+        return value
+    return None

venv/lib/python3.11/site-packages/mypy/copytype.py

@@ -0,0 +1,134 @@
+from __future__ import annotations
+
+from typing import Any, cast
+
+from mypy.types import (
+    AnyType,
+    CallableType,
+    DeletedType,
+    ErasedType,
+    Instance,
+    LiteralType,
+    NoneType,
+    Overloaded,
+    Parameters,
+    ParamSpecType,
+    PartialType,
+    ProperType,
+    TupleType,
+    TypeAliasType,
+    TypedDictType,
+    TypeType,
+    TypeVarTupleType,
+    TypeVarType,
+    UnboundType,
+    UninhabitedType,
+    UnionType,
+    UnpackType,
+)
+
+# type_visitor needs to be imported after types
+from mypy.type_visitor import TypeVisitor  # ruff: isort: skip
+
+
+def copy_type(t: ProperType) -> ProperType:
+    """Create a shallow copy of a type.
+
+    This can be used to mutate the copy with truthiness information.
+
+    Classes compiled with mypyc don't support copy.copy(), so we need
+    a custom implementation.
+    """
+    return t.accept(TypeShallowCopier())
+
+
+class TypeShallowCopier(TypeVisitor[ProperType]):
+    def visit_unbound_type(self, t: UnboundType) -> ProperType:
+        return t
+
+    def visit_any(self, t: AnyType) -> ProperType:
+        return self.copy_common(t, AnyType(t.type_of_any, t.source_any, t.missing_import_name))
+
+    def visit_none_type(self, t: NoneType) -> ProperType:
+        return self.copy_common(t, NoneType())
+
+    def visit_uninhabited_type(self, t: UninhabitedType) -> ProperType:
+        dup = UninhabitedType()
+        dup.ambiguous = t.ambiguous
+        return self.copy_common(t, dup)
+
+    def visit_erased_type(self, t: ErasedType) -> ProperType:
+        return self.copy_common(t, ErasedType())
+
+    def visit_deleted_type(self, t: DeletedType) -> ProperType:
+        return self.copy_common(t, DeletedType(t.source))
+
+    def visit_instance(self, t: Instance) -> ProperType:
+        dup = Instance(t.type, t.args, last_known_value=t.last_known_value)
+        return self.copy_common(t, dup)
+
+    def visit_type_var(self, t: TypeVarType) -> ProperType:
+        return self.copy_common(t, t.copy_modified())
+
+    def visit_param_spec(self, t: ParamSpecType) -> ProperType:
+        dup = ParamSpecType(
+            t.name, t.fullname, t.id, t.flavor, t.upper_bound, t.default, prefix=t.prefix
+        )
+        return self.copy_common(t, dup)
+
+    def visit_parameters(self, t: Parameters) -> ProperType:
+        dup = Parameters(
+            t.arg_types,
+            t.arg_kinds,
+            t.arg_names,
+            variables=t.variables,
+            is_ellipsis_args=t.is_ellipsis_args,
+        )
+        return self.copy_common(t, dup)
+
+    def visit_type_var_tuple(self, t: TypeVarTupleType) -> ProperType:
+        dup = TypeVarTupleType(
+            t.name, t.fullname, t.id, t.upper_bound, t.tuple_fallback, t.default
+        )
+        return self.copy_common(t, dup)
+
+    def visit_unpack_type(self, t: UnpackType) -> ProperType:
+        dup = UnpackType(t.type)
+        return self.copy_common(t, dup)
+
+    def visit_partial_type(self, t: PartialType) -> ProperType:
+        return self.copy_common(t, PartialType(t.type, t.var, t.value_type))
+
+    def visit_callable_type(self, t: CallableType) -> ProperType:
+        return self.copy_common(t, t.copy_modified())
+
+    def visit_tuple_type(self, t: TupleType) -> ProperType:
+        return self.copy_common(t, TupleType(t.items, t.partial_fallback, implicit=t.implicit))
+
+    def visit_typeddict_type(self, t: TypedDictType) -> ProperType:
+        return self.copy_common(
+            t, TypedDictType(t.items, t.required_keys, t.readonly_keys, t.fallback)
+        )
+
+    def visit_literal_type(self, t: LiteralType) -> ProperType:
+        return self.copy_common(t, LiteralType(value=t.value, fallback=t.fallback))
+
+    def visit_union_type(self, t: UnionType) -> ProperType:
+        return self.copy_common(t, UnionType(t.items))
+
+    def visit_overloaded(self, t: Overloaded) -> ProperType:
+        return self.copy_common(t, Overloaded(items=t.items))
+
+    def visit_type_type(self, t: TypeType) -> ProperType:
+        # Use cast since the type annotations in TypeType are imprecise.
+        return self.copy_common(t, TypeType(cast(Any, t.item), is_type_form=t.is_type_form))
+
+    def visit_type_alias_type(self, t: TypeAliasType) -> ProperType:
+        assert False, "only ProperTypes supported"
+
+    def copy_common(self, t: ProperType, t2: ProperType) -> ProperType:
+        t2.line = t.line
+        t2.column = t.column
+        t2.can_be_false = t.can_be_false
+        t2.can_be_true = t.can_be_true
+        return t2

venv/lib/python3.11/site-packages/mypy/defaults.py

@@ -0,0 +1,51 @@
+from __future__ import annotations
+
+import os
+from typing import Final
+
+# Earliest fully supported Python 3.x version. Used as the default Python
+# version in tests. Mypy wheels should be built starting with this version,
+# and CI tests should be run on this version (and later versions).
+PYTHON3_VERSION: Final = (3, 10)
+
+# Earliest Python 3.x version supported via --python-version 3.x. To run
+# mypy, at least version PYTHON3_VERSION is needed.
+PYTHON3_VERSION_MIN: Final = (3, 9)  # Keep in sync with typeshed's python support
+
+CACHE_DIR: Final = ".mypy_cache"
+
+CONFIG_NAMES: Final = ["mypy.ini", ".mypy.ini"]
+SHARED_CONFIG_NAMES: Final = ["pyproject.toml", "setup.cfg"]
+
+USER_CONFIG_FILES: list[str] = ["~/.config/mypy/config", "~/.mypy.ini"]
+if os.environ.get("XDG_CONFIG_HOME"):
+    USER_CONFIG_FILES.insert(0, os.path.join(os.environ["XDG_CONFIG_HOME"], "mypy/config"))
+USER_CONFIG_FILES = [os.path.expanduser(f) for f in USER_CONFIG_FILES]
+
+# This must include all reporters defined in mypy.report. This is defined here
+# to make reporter names available without importing mypy.report -- this speeds
+# up startup.
+REPORTER_NAMES: Final = [
+    "linecount",
+    "any-exprs",
+    "linecoverage",
+    "memory-xml",
+    "cobertura-xml",
+    "xml",
+    "xslt-html",
+    "xslt-txt",
+    "html",
+    "txt",
+    "lineprecision",
+]
+
+# Threshold after which we sometimes filter out most errors to avoid very
+# verbose output. The default is to show all errors.
+MANY_ERRORS_THRESHOLD: Final = -1
+
+RECURSION_LIMIT: Final = 2**14
+
+WORKER_START_INTERVAL: Final = 0.01
+WORKER_START_TIMEOUT: Final = 3
+WORKER_CONNECTION_TIMEOUT: Final = 10
+WORKER_DONE_TIMEOUT: Final = 600

venv/lib/python3.11/site-packages/mypy/dmypy/__main__.py

@@ -0,0 +1,6 @@
+from __future__ import annotations
+
+from mypy.dmypy.client import console_entry
+
+if __name__ == "__main__":
+    console_entry()

venv/lib/python3.11/site-packages/mypy/dmypy/client.py

@@ -0,0 +1,732 @@
+"""Client for mypy daemon mode.
+
+This manages a daemon process which keeps useful state in memory
+rather than having to read it back from disk on each run.
+"""
+
+from __future__ import annotations
+
+import argparse
+import json
+import os
+import pickle
+import sys
+import time
+import traceback
+from collections.abc import Callable, Mapping
+from typing import Any, NoReturn
+
+from librt.base64 import b64decode
+
+from mypy.defaults import RECURSION_LIMIT
+from mypy.dmypy_os import alive, kill
+from mypy.dmypy_util import DEFAULT_STATUS_FILE, receive, send
+from mypy.ipc import BadStatus, IPCClient, IPCException, read_status
+from mypy.util import check_python_version, get_terminal_width, should_force_color
+from mypy.version import __version__
+
+# Argument parser.  Subparsers are tied to action functions by the
+# @action(subparse) decorator.
+
+
+class AugmentedHelpFormatter(argparse.RawDescriptionHelpFormatter):
+    def __init__(self, prog: str, **kwargs: Any) -> None:
+        super().__init__(prog=prog, max_help_position=30, **kwargs)
+
+
+parser = argparse.ArgumentParser(
+    prog="dmypy", description="Client for mypy daemon mode", fromfile_prefix_chars="@"
+)
+parser.set_defaults(action=None)
+parser.add_argument(
+    "--status-file", default=DEFAULT_STATUS_FILE, help="status file to retrieve daemon details"
+)
+parser.add_argument(
+    "-V",
+    "--version",
+    action="version",
+    version="%(prog)s " + __version__,
+    help="Show program's version number and exit",
+)
+subparsers = parser.add_subparsers()
+
+start_parser = p = subparsers.add_parser("start", help="Start daemon")
+p.add_argument("--log-file", metavar="FILE", type=str, help="Direct daemon stdout/stderr to FILE")
+p.add_argument(
+    "--timeout", metavar="TIMEOUT", type=int, help="Server shutdown timeout (in seconds)"
+)
+p.add_argument(
+    "flags", metavar="FLAG", nargs="*", type=str, help="Regular mypy flags (precede with --)"
+)
+
+restart_parser = p = subparsers.add_parser(
+    "restart", help="Restart daemon (stop or kill followed by start)"
+)
+p.add_argument("--log-file", metavar="FILE", type=str, help="Direct daemon stdout/stderr to FILE")
+p.add_argument(
+    "--timeout", metavar="TIMEOUT", type=int, help="Server shutdown timeout (in seconds)"
+)
+p.add_argument(
+    "flags", metavar="FLAG", nargs="*", type=str, help="Regular mypy flags (precede with --)"
+)
+
+status_parser = p = subparsers.add_parser("status", help="Show daemon status")
+p.add_argument("-v", "--verbose", action="store_true", help="Print detailed status")
+p.add_argument("--fswatcher-dump-file", help="Collect information about the current file state")
+
+stop_parser = p = subparsers.add_parser("stop", help="Stop daemon (asks it politely to go away)")
+
+kill_parser = p = subparsers.add_parser("kill", help="Kill daemon (kills the process)")
+
+check_parser = p = subparsers.add_parser(
+    "check", formatter_class=AugmentedHelpFormatter, help="Check some files (requires daemon)"
+)
+p.add_argument("-v", "--verbose", action="store_true", help="Print detailed status")
+p.add_argument("-q", "--quiet", action="store_true", help=argparse.SUPPRESS)  # Deprecated
+p.add_argument("--junit-xml", help="Write junit.xml to the given file")
+p.add_argument("--perf-stats-file", help="write performance information to the given file")
+p.add_argument("files", metavar="FILE", nargs="+", help="File (or directory) to check")
+p.add_argument(
+    "--export-types",
+    action="store_true",
+    help="Store types of all expressions in a shared location (useful for inspections)",
+)
+
+run_parser = p = subparsers.add_parser(
+    "run",
+    formatter_class=AugmentedHelpFormatter,
+    help="Check some files, [re]starting daemon if necessary",
+)
+p.add_argument("-v", "--verbose", action="store_true", help="Print detailed status")
+p.add_argument("--junit-xml", help="Write junit.xml to the given file")
+p.add_argument("--perf-stats-file", help="write performance information to the given file")
+p.add_argument(
+    "--timeout", metavar="TIMEOUT", type=int, help="Server shutdown timeout (in seconds)"
+)
+p.add_argument("--log-file", metavar="FILE", type=str, help="Direct daemon stdout/stderr to FILE")
+p.add_argument(
+    "--export-types",
+    action="store_true",
+    help="Store types of all expressions in a shared location (useful for inspections)",
+)
+p.add_argument(
+    "flags",
+    metavar="ARG",
+    nargs="*",
+    type=str,
+    help="Regular mypy flags and files (precede with --)",
+)
+
+recheck_parser = p = subparsers.add_parser(
+    "recheck",
+    formatter_class=AugmentedHelpFormatter,
+    help="Re-check the previous list of files, with optional modifications (requires daemon)",
+)
+p.add_argument("-v", "--verbose", action="store_true", help="Print detailed status")
+p.add_argument("-q", "--quiet", action="store_true", help=argparse.SUPPRESS)  # Deprecated
+p.add_argument("--junit-xml", help="Write junit.xml to the given file")
+p.add_argument("--perf-stats-file", help="write performance information to the given file")
+p.add_argument(
+    "--export-types",
+    action="store_true",
+    help="Store types of all expressions in a shared location (useful for inspections)",
+)
+p.add_argument(
+    "--update",
+    metavar="FILE",
+    nargs="*",
+    help="Files in the run to add or check again (default: all from previous run)",
+)
+p.add_argument("--remove", metavar="FILE", nargs="*", help="Files to remove from the run")
+
+suggest_parser = p = subparsers.add_parser(
+    "suggest", help="Suggest a signature or show call sites for a specific function"
+)
+p.add_argument(
+    "function",
+    metavar="FUNCTION",
+    type=str,
+    help="Function specified as '[package.]module.[class.]function'",
+)
+p.add_argument(
+    "--json",
+    action="store_true",
+    help="Produce json that pyannotate can use to apply a suggestion",
+)
+p.add_argument(
+    "--no-errors", action="store_true", help="Only produce suggestions that cause no errors"
+)
+p.add_argument(
+    "--no-any", action="store_true", help="Only produce suggestions that don't contain Any"
+)
+p.add_argument(
+    "--flex-any",
+    type=float,
+    help="Allow anys in types if they go above a certain score (scores are from 0-1)",
+)
+p.add_argument(
+    "--callsites", action="store_true", help="Find callsites instead of suggesting a type"
+)
+p.add_argument(
+    "--use-fixme",
+    metavar="NAME",
+    type=str,
+    help="A dummy name to use instead of Any for types that can't be inferred",
+)
+p.add_argument(
+    "--max-guesses",
+    type=int,
+    help="Set the maximum number of types to try for a function (default 64)",
+)
+
+inspect_parser = p = subparsers.add_parser(
+    "inspect", help="Locate and statically inspect expression(s)"
+)
+p.add_argument(
+    "location",
+    metavar="LOCATION",
+    type=str,
+    help="Location specified as path/to/file.py:line:column[:end_line:end_column]."
+    " If position is given (i.e. only line and column), this will return all"
+    " enclosing expressions",
+)
+p.add_argument(
+    "--show",
+    metavar="INSPECTION",
+    type=str,
+    default="type",
+    choices=["type", "attrs", "definition"],
+    help="What kind of inspection to run",
+)
+p.add_argument(
+    "--verbose",
+    "-v",
+    action="count",
+    default=0,
+    help="Increase verbosity of the type string representation (can be repeated)",
+)
+p.add_argument(
+    "--limit",
+    metavar="NUM",
+    type=int,
+    default=0,
+    help="Return at most NUM innermost expressions (if position is given); 0 means no limit",
+)
+p.add_argument(
+    "--include-span",
+    action="store_true",
+    help="Prepend each inspection result with the span of corresponding expression"
+    ' (e.g. 1:2:3:4:"int")',
+)
+p.add_argument(
+    "--include-kind",
+    action="store_true",
+    help="Prepend each inspection result with the kind of corresponding expression"
+    ' (e.g. NameExpr:"int")',
+)
+p.add_argument(
+    "--include-object-attrs",
+    action="store_true",
+    help='Include attributes of "object" in "attrs" inspection',
+)
+p.add_argument(
+    "--union-attrs",
+    action="store_true",
+    help="Include attributes valid for some of possible expression types"
+    " (by default an intersection is returned)",
+)
+p.add_argument(
+    "--force-reload",
+    action="store_true",
+    help="Re-parse and re-type-check file before inspection (may be slow)",
+)
+
+hang_parser = p = subparsers.add_parser("hang", help="Hang for 100 seconds")
+
+daemon_parser = p = subparsers.add_parser("daemon", help="Run daemon in foreground")
+p.add_argument(
+    "--timeout", metavar="TIMEOUT", type=int, help="Server shutdown timeout (in seconds)"
+)
+p.add_argument("--log-file", metavar="FILE", type=str, help="Direct daemon stdout/stderr to FILE")
+p.add_argument(
+    "flags", metavar="FLAG", nargs="*", type=str, help="Regular mypy flags (precede with --)"
+)
+p.add_argument("--options-data", help=argparse.SUPPRESS)
+help_parser = p = subparsers.add_parser("help")
+
+del p
+
+
+def main(argv: list[str]) -> None:
+    """The code is top-down."""
+    check_python_version("dmypy")
+
+    # set recursion limit consistent with mypy/main.py
+    sys.setrecursionlimit(RECURSION_LIMIT)
+
+    args = parser.parse_args(argv)
+    if not args.action:
+        parser.print_usage()
+    else:
+        try:
+            args.action(args)
+        except BadStatus as err:
+            fail(err.args[0])
+        except Exception:
+            # We do this explicitly to avoid exceptions percolating up
+            # through mypy.api invocations
+            traceback.print_exc()
+            sys.exit(2)
+
+
+def fail(msg: str) -> NoReturn:
+    print(msg, file=sys.stderr)
+    sys.exit(2)
+
+
+ActionFunction = Callable[[argparse.Namespace], None]
+
+
+def action(subparser: argparse.ArgumentParser) -> Callable[[ActionFunction], ActionFunction]:
+    """Decorator to tie an action function to a subparser."""
+
+    def register(func: ActionFunction) -> ActionFunction:
+        subparser.set_defaults(action=func)
+        return func
+
+    return register
+
+
+# Action functions (run in client from command line).
+
+
+@action(start_parser)
+def do_start(args: argparse.Namespace) -> None:
+    """Start daemon (it must not already be running).
+
+    This is where mypy flags are set from the command line.
+
+    Setting flags is a bit awkward; you have to use e.g.:
+
+      dmypy start -- --strict
+
+    since we don't want to duplicate mypy's huge list of flags.
+    """
+    try:
+        get_status(args.status_file)
+    except BadStatus:
+        # Bad or missing status file or dead process; good to start.
+        pass
+    else:
+        fail("Daemon is still alive")
+    start_server(args)
+
+
+@action(restart_parser)
+def do_restart(args: argparse.Namespace) -> None:
+    """Restart daemon (it may or may not be running; but not hanging).
+
+    We first try to stop it politely if it's running.  This also sets
+    mypy flags from the command line (see do_start()).
+    """
+    restart_server(args)
+
+
+def restart_server(args: argparse.Namespace, allow_sources: bool = False) -> None:
+    """Restart daemon (it may or may not be running; but not hanging)."""
+    try:
+        do_stop(args)
+    except BadStatus:
+        # Bad or missing status file or dead process; good to start.
+        pass
+    start_server(args, allow_sources)
+
+
+def start_server(args: argparse.Namespace, allow_sources: bool = False) -> None:
+    """Start the server from command arguments and wait for it."""
+    # Lazy import so this import doesn't slow down other commands.
+    from mypy.dmypy_server import daemonize, process_start_options
+
+    start_options = process_start_options(args.flags, allow_sources)
+    if daemonize(start_options, args.status_file, timeout=args.timeout, log_file=args.log_file):
+        sys.exit(2)
+    wait_for_server(args.status_file)
+
+
+def wait_for_server(status_file: str, timeout: float = 5.0) -> None:
+    """Wait until the server is up.
+
+    Exit if it doesn't happen within the timeout.
+    """
+    endtime = time.time() + timeout
+    while time.time() < endtime:
+        try:
+            data = read_status(status_file)
+        except BadStatus:
+            # If the file isn't there yet, retry later.
+            time.sleep(0.1)
+            continue
+        # If the file's content is bogus or the process is dead, fail.
+        check_status(data)
+        print("Daemon started")
+        return
+    fail("Timed out waiting for daemon to start")
+
+
+@action(run_parser)
+def do_run(args: argparse.Namespace) -> None:
+    """Do a check, starting (or restarting) the daemon as necessary
+
+    Restarts the daemon if the running daemon reports that it is
+    required (due to a configuration change, for example).
+
+    Setting flags is a bit awkward; you have to use e.g.:
+
+      dmypy run -- --strict a.py b.py ...
+
+    since we don't want to duplicate mypy's huge list of flags.
+    (The -- is only necessary if flags are specified.)
+    """
+    if not is_running(args.status_file):
+        # Bad or missing status file or dead process; good to start.
+        start_server(args, allow_sources=True)
+    t0 = time.time()
+    response = request(
+        args.status_file,
+        "run",
+        version=__version__,
+        args=args.flags,
+        export_types=args.export_types,
+    )
+    # If the daemon signals that a restart is necessary, do it
+    if "restart" in response:
+        print(f"Restarting: {response['restart']}")
+        restart_server(args, allow_sources=True)
+        response = request(
+            args.status_file,
+            "run",
+            version=__version__,
+            args=args.flags,
+            export_types=args.export_types,
+        )
+
+    t1 = time.time()
+    response["roundtrip_time"] = t1 - t0
+    check_output(response, args.verbose, args.junit_xml, args.perf_stats_file)
+
+
+@action(status_parser)
+def do_status(args: argparse.Namespace) -> None:
+    """Print daemon status.
+
+    This verifies that it is responsive to requests.
+    """
+    status = read_status(args.status_file)
+    if args.verbose:
+        show_stats(status)
+    # Both check_status() and request() may raise BadStatus,
+    # which will be handled by main().
+    check_status(status)
+    response = request(
+        args.status_file, "status", fswatcher_dump_file=args.fswatcher_dump_file, timeout=5
+    )
+    if args.verbose or "error" in response:
+        show_stats(response)
+    if "error" in response:
+        fail(f"Daemon may be busy processing; if this persists, consider {sys.argv[0]} kill")
+    print("Daemon is up and running")
+
+
+@action(stop_parser)
+def do_stop(args: argparse.Namespace) -> None:
+    """Stop daemon via a 'stop' request."""
+    # May raise BadStatus, which will be handled by main().
+    response = request(args.status_file, "stop", timeout=5)
+    if "error" in response:
+        show_stats(response)
+        fail(f"Daemon may be busy processing; if this persists, consider {sys.argv[0]} kill")
+    else:
+        print("Daemon stopped")
+
+
+@action(kill_parser)
+def do_kill(args: argparse.Namespace) -> None:
+    """Kill daemon process with SIGKILL."""
+    pid, _ = get_status(args.status_file)
+    try:
+        kill(pid)
+    except OSError as err:
+        fail(str(err))
+    else:
+        print("Daemon killed")
+
+
+@action(check_parser)
+def do_check(args: argparse.Namespace) -> None:
+    """Ask the daemon to check a list of files."""
+    t0 = time.time()
+    response = request(args.status_file, "check", files=args.files, export_types=args.export_types)
+    t1 = time.time()
+    response["roundtrip_time"] = t1 - t0
+    check_output(response, args.verbose, args.junit_xml, args.perf_stats_file)
+
+
+@action(recheck_parser)
+def do_recheck(args: argparse.Namespace) -> None:
+    """Ask the daemon to recheck the previous list of files, with optional modifications.
+
+    If at least one of --remove or --update is given, the server will
+    update the list of files to check accordingly and assume that any other files
+    are unchanged.  If none of these flags are given, the server will call stat()
+    on each file last checked to determine its status.
+
+    Files given in --update ought to exist.  Files given in --remove need not exist;
+    if they don't they will be ignored.
+    The lists may be empty but oughtn't contain duplicates or overlap.
+
+    NOTE: The list of files is lost when the daemon is restarted.
+    """
+    t0 = time.time()
+    if args.remove is not None or args.update is not None:
+        response = request(
+            args.status_file,
+            "recheck",
+            export_types=args.export_types,
+            remove=args.remove,
+            update=args.update,
+        )
+    else:
+        response = request(args.status_file, "recheck", export_types=args.export_types)
+    t1 = time.time()
+    response["roundtrip_time"] = t1 - t0
+    check_output(response, args.verbose, args.junit_xml, args.perf_stats_file)
+
+
+@action(suggest_parser)
+def do_suggest(args: argparse.Namespace) -> None:
+    """Ask the daemon for a suggested signature.
+
+    This just prints whatever the daemon reports as output.
+    For now it may be closer to a list of call sites.
+    """
+    response = request(
+        args.status_file,
+        "suggest",
+        function=args.function,
+        json=args.json,
+        callsites=args.callsites,
+        no_errors=args.no_errors,
+        no_any=args.no_any,
+        flex_any=args.flex_any,
+        use_fixme=args.use_fixme,
+        max_guesses=args.max_guesses,
+    )
+    check_output(response, verbose=False, junit_xml=None, perf_stats_file=None)
+
+
+@action(inspect_parser)
+def do_inspect(args: argparse.Namespace) -> None:
+    """Ask daemon to print the type of an expression."""
+    response = request(
+        args.status_file,
+        "inspect",
+        show=args.show,
+        location=args.location,
+        verbosity=args.verbose,
+        limit=args.limit,
+        include_span=args.include_span,
+        include_kind=args.include_kind,
+        include_object_attrs=args.include_object_attrs,
+        union_attrs=args.union_attrs,
+        force_reload=args.force_reload,
+    )
+    check_output(response, verbose=False, junit_xml=None, perf_stats_file=None)
+
+
+def check_output(
+    response: dict[str, Any], verbose: bool, junit_xml: str | None, perf_stats_file: str | None
+) -> None:
+    """Print the output from a check or recheck command.
+
+    Call sys.exit() unless the status code is zero.
+    """
+    if os.name == "nt":
+        # Enable ANSI color codes for Windows cmd using this strange workaround
+        # ( see https://github.com/python/cpython/issues/74261 )
+        os.system("")
+    if "error" in response:
+        fail(response["error"])
+    try:
+        out, err, status_code = response["out"], response["err"], response["status"]
+    except KeyError:
+        fail(f"Response: {str(response)}")
+    sys.stdout.write(out)
+    sys.stdout.flush()
+    sys.stderr.write(err)
+    sys.stderr.flush()
+    if verbose:
+        show_stats(response)
+    if junit_xml:
+        # Lazy import so this import doesn't slow things down when not writing junit
+        from mypy.util import write_junit_xml
+
+        messages = (out + err).splitlines()
+        write_junit_xml(
+            response["roundtrip_time"],
+            bool(err),
+            {None: messages} if messages else {},
+            junit_xml,
+            response["python_version"],
+            response["platform"],
+        )
+    if perf_stats_file:
+        telemetry = response.get("stats", {})
+        with open(perf_stats_file, "w") as f:
+            json.dump(telemetry, f)
+
+    if status_code:
+        sys.exit(status_code)
+
+
+def show_stats(response: Mapping[str, object]) -> None:
+    for key, value in sorted(response.items()):
+        if key in ("out", "err", "stdout", "stderr"):
+            # Special case text output to display just 40 characters of text
+            value = repr(value)[1:-1]
+            if len(value) > 50:
+                value = f"{value[:40]} ... {len(value)-40} more characters"
+            print("%-24s: %s" % (key, value))
+            continue
+        print("%-24s: %10s" % (key, "%.3f" % value if isinstance(value, float) else value))
+
+
+@action(hang_parser)
+def do_hang(args: argparse.Namespace) -> None:
+    """Hang for 100 seconds, as a debug hack."""
+    print(request(args.status_file, "hang", timeout=1))
+
+
+@action(daemon_parser)
+def do_daemon(args: argparse.Namespace) -> None:
+    """Serve requests in the foreground."""
+    # Lazy import so this import doesn't slow down other commands.
+    from mypy.dmypy_server import Server, process_start_options
+
+    if args.log_file:
+        sys.stdout = sys.stderr = open(args.log_file, "a", buffering=1)
+        fd = sys.stdout.fileno()
+        os.dup2(fd, 2)
+        os.dup2(fd, 1)
+
+    if args.options_data:
+        from mypy.options import Options
+
+        options_dict = pickle.loads(b64decode(args.options_data))
+        options_obj = Options()
+        options = options_obj.apply_changes(options_dict)
+    else:
+        options = process_start_options(args.flags, allow_sources=False)
+
+    Server(options, args.status_file, timeout=args.timeout).serve()
+
+
+@action(help_parser)
+def do_help(args: argparse.Namespace) -> None:
+    """Print full help (same as dmypy --help)."""
+    parser.print_help()
+
+
+# Client-side infrastructure.
+
+
+def request(
+    status_file: str, command: str, *, timeout: int | None = None, **kwds: object
+) -> dict[str, Any]:
+    """Send a request to the daemon.
+
+    Return the JSON dict with the response.
+
+    Raise BadStatus if there is something wrong with the status file
+    or if the process whose pid is in the status file has died.
+
+    Return {'error': <message>} if an IPC operation or receive()
+    raised OSError.  This covers cases such as connection refused or
+    closed prematurely as well as invalid JSON received.
+    """
+    response: dict[str, str] = {}
+    args = dict(kwds)
+    args["command"] = command
+    # Tell the server whether this request was initiated from a human-facing terminal,
+    # so that it can format the type checking output accordingly.
+    args["is_tty"] = sys.stdout.isatty() or should_force_color()
+    args["terminal_width"] = get_terminal_width()
+    _, name = get_status(status_file)
+    try:
+        with IPCClient(name, timeout) as client:
+            send(client, args)
+
+            final = False
+            while not final:
+                response = receive(client)
+                final = bool(response.pop("final", False))
+                # Display debugging output written to stdout/stderr in the server process for convenience.
+                # This should not be confused with "out" and "err" fields in the response.
+                # Those fields hold the output of the "check" command, and are handled in check_output().
+                stdout = response.pop("stdout", None)
+                if stdout:
+                    sys.stdout.write(stdout)
+                stderr = response.pop("stderr", None)
+                if stderr:
+                    sys.stderr.write(stderr)
+    except (OSError, IPCException) as err:
+        return {"error": str(err)}
+    # TODO: Other errors, e.g. ValueError, UnicodeError
+
+    return response
+
+
+def get_status(status_file: str) -> tuple[int, str]:
+    """Read status file and check if the process is alive.
+
+    Return (pid, connection_name) on success.
+
+    Raise BadStatus if something's wrong.
+    """
+    data = read_status(status_file)
+    return check_status(data)
+
+
+def check_status(data: dict[str, Any]) -> tuple[int, str]:
+    """Check if the process is alive.
+
+    Return (pid, connection_name) on success.
+
+    Raise BadStatus if something's wrong.
+    """
+    if "pid" not in data:
+        raise BadStatus("Invalid status file (no pid field)")
+    pid = data["pid"]
+    if not isinstance(pid, int):
+        raise BadStatus("pid field is not an int")
+    if not alive(pid):
+        raise BadStatus("Daemon has died")
+    if "connection_name" not in data:
+        raise BadStatus("Invalid status file (no connection_name field)")
+    connection_name = data["connection_name"]
+    if not isinstance(connection_name, str):
+        raise BadStatus("connection_name field is not a string")
+    return pid, connection_name
+
+
+def is_running(status_file: str) -> bool:
+    """Check if the server is running cleanly"""
+    try:
+        get_status(status_file)
+    except BadStatus:
+        return False
+    return True
+
+
+# Run main().
+def console_entry() -> None:
+    main(sys.argv[1:])

venv/lib/python3.11/site-packages/mypy/dmypy_os.py

@@ -0,0 +1,43 @@
+from __future__ import annotations
+
+import sys
+from collections.abc import Callable
+from typing import Any
+
+if sys.platform == "win32":
+    import ctypes
+    import subprocess
+    from ctypes.wintypes import DWORD, HANDLE
+
+    PROCESS_QUERY_LIMITED_INFORMATION = ctypes.c_ulong(0x1000)
+
+    kernel32 = ctypes.windll.kernel32
+    OpenProcess: Callable[[DWORD, int, int], HANDLE] = kernel32.OpenProcess
+    GetExitCodeProcess: Callable[[HANDLE, Any], int] = kernel32.GetExitCodeProcess
+else:
+    import os
+    import signal
+
+
+def alive(pid: int) -> bool:
+    """Is the process alive?"""
+    if sys.platform == "win32":
+        # why can't anything be easy...
+        status = DWORD()
+        handle = OpenProcess(PROCESS_QUERY_LIMITED_INFORMATION, 0, pid)
+        GetExitCodeProcess(handle, ctypes.byref(status))
+        return status.value == 259  # STILL_ACTIVE
+    else:
+        try:
+            os.kill(pid, 0)
+        except OSError:
+            return False
+        return True
+
+
+def kill(pid: int) -> None:
+    """Kill the process."""
+    if sys.platform == "win32":
+        subprocess.check_output(f"taskkill /pid {pid} /f /t")
+    else:
+        os.kill(pid, signal.SIGKILL)

venv/lib/python3.11/site-packages/mypy/dmypy_util.py

@@ -0,0 +1,117 @@
+"""Shared code between dmypy.py and dmypy_server.py.
+
+This should be pretty lightweight and not depend on other mypy code (other than ipc).
+"""
+
+from __future__ import annotations
+
+import io
+import json
+from collections.abc import Iterable, Iterator
+from types import TracebackType
+from typing import Any, Final, TextIO
+
+from mypy.ipc import IPCBase
+
+DEFAULT_STATUS_FILE: Final = ".dmypy.json"
+
+
+def receive(connection: IPCBase) -> Any:
+    """Receive single JSON data frame from a connection.
+
+    Raise OSError if the data received is not valid JSON or if it is
+    not a dict.
+    """
+    bdata = connection.read()
+    if not bdata:
+        raise OSError("No data received")
+    try:
+        data = json.loads(bdata)
+    except Exception as e:
+        raise OSError("Data received is not valid JSON") from e
+    if not isinstance(data, dict):
+        raise OSError(f"Data received is not a dict ({type(data)})")
+    return data
+
+
+def send(connection: IPCBase, data: Any) -> None:
+    """Send data to a connection encoded and framed.
+
+    The data must be JSON-serializable. We assume that a single send call is a
+    single frame to be sent on the connect.
+    """
+    connection.write(json.dumps(data))
+
+
+class WriteToConn(TextIO):
+    """Helper class to write to a connection instead of standard output."""
+
+    def __init__(self, server: IPCBase, output_key: str, isatty: bool) -> None:
+        self.server = server
+        self.output_key = output_key
+        self._isatty = isatty
+
+    def __enter__(self) -> TextIO:
+        return self
+
+    def __exit__(
+        self,
+        t: type[BaseException] | None,
+        value: BaseException | None,
+        traceback: TracebackType | None,
+    ) -> None:
+        pass
+
+    def __iter__(self) -> Iterator[str]:
+        raise io.UnsupportedOperation
+
+    def __next__(self) -> str:
+        raise io.UnsupportedOperation
+
+    def close(self) -> None:
+        pass
+
+    def fileno(self) -> int:
+        raise OSError
+
+    def flush(self) -> None:
+        pass
+
+    def isatty(self) -> bool:
+        return self._isatty
+
+    def read(self, n: int = 0) -> str:
+        raise io.UnsupportedOperation
+
+    def readable(self) -> bool:
+        return False
+
+    def readline(self, limit: int = 0) -> str:
+        raise io.UnsupportedOperation
+
+    def readlines(self, hint: int = 0) -> list[str]:
+        raise io.UnsupportedOperation
+
+    def seek(self, offset: int, whence: int = 0) -> int:
+        raise io.UnsupportedOperation
+
+    def seekable(self) -> bool:
+        return False
+
+    def tell(self) -> int:
+        raise io.UnsupportedOperation
+
+    def truncate(self, size: int | None = 0) -> int:
+        raise io.UnsupportedOperation
+
+    def write(self, output: str) -> int:
+        resp: dict[str, Any] = {self.output_key: output}
+        send(self.server, resp)
+        return len(output)
+
+    def writable(self) -> bool:
+        return True
+
+    def writelines(self, lines: Iterable[str]) -> None:
+        for s in lines:
+            self.write(s)

venv/lib/python3.11/site-packages/mypy/erasetype.py

@@ -0,0 +1,301 @@
+from __future__ import annotations
+
+from collections.abc import Callable, Container
+from typing import cast
+
+from mypy.nodes import ARG_STAR, ARG_STAR2
+from mypy.types import (
+    AnyType,
+    CallableType,
+    DeletedType,
+    ErasedType,
+    Instance,
+    LiteralType,
+    NoneType,
+    Overloaded,
+    Parameters,
+    ParamSpecType,
+    PartialType,
+    ProperType,
+    TupleType,
+    Type,
+    TypeAliasType,
+    TypedDictType,
+    TypeOfAny,
+    TypeTranslator,
+    TypeType,
+    TypeVarId,
+    TypeVarTupleType,
+    TypeVarType,
+    TypeVisitor,
+    UnboundType,
+    UninhabitedType,
+    UnionType,
+    UnpackType,
+    get_proper_type,
+    get_proper_types,
+)
+from mypy.typevartuples import erased_vars
+
+
+def erase_type(typ: Type) -> ProperType:
+    """Erase any type variables from a type.
+
+    Also replace tuple types with the corresponding concrete types.
+
+    Examples:
+      A -> A
+      B[X] -> B[Any]
+      Tuple[A, B] -> tuple
+      Callable[[A1, A2, ...], R] -> Callable[..., Any]
+      Type[X] -> Type[Any]
+    """
+    typ = get_proper_type(typ)
+    return typ.accept(EraseTypeVisitor())
+
+
+class EraseTypeVisitor(TypeVisitor[ProperType]):
+    def visit_unbound_type(self, t: UnboundType) -> ProperType:
+        # TODO: replace with an assert after UnboundType can't leak from semantic analysis.
+        return AnyType(TypeOfAny.from_error)
+
+    def visit_any(self, t: AnyType) -> ProperType:
+        return t
+
+    def visit_none_type(self, t: NoneType) -> ProperType:
+        return t
+
+    def visit_uninhabited_type(self, t: UninhabitedType) -> ProperType:
+        return t
+
+    def visit_erased_type(self, t: ErasedType) -> ProperType:
+        return t
+
+    def visit_partial_type(self, t: PartialType) -> ProperType:
+        # Should not get here.
+        raise RuntimeError("Cannot erase partial types")
+
+    def visit_deleted_type(self, t: DeletedType) -> ProperType:
+        return t
+
+    def visit_instance(self, t: Instance) -> ProperType:
+        args = erased_vars(t.type.defn.type_vars, TypeOfAny.special_form)
+        return Instance(t.type, args, t.line)
+
+    def visit_type_var(self, t: TypeVarType) -> ProperType:
+        return AnyType(TypeOfAny.special_form)
+
+    def visit_param_spec(self, t: ParamSpecType) -> ProperType:
+        return AnyType(TypeOfAny.special_form)
+
+    def visit_parameters(self, t: Parameters) -> ProperType:
+        raise RuntimeError("Parameters should have been bound to a class")
+
+    def visit_type_var_tuple(self, t: TypeVarTupleType) -> ProperType:
+        # Likely, we can never get here because of aggressive erasure of types that
+        # can contain this, but better still return a valid replacement.
+        return t.tuple_fallback.copy_modified(args=[AnyType(TypeOfAny.special_form)])
+
+    def visit_unpack_type(self, t: UnpackType) -> ProperType:
+        return AnyType(TypeOfAny.special_form)
+
+    def visit_callable_type(self, t: CallableType) -> ProperType:
+        # We must preserve the fallback type for overload resolution to work.
+        any_type = AnyType(TypeOfAny.special_form)
+        return CallableType(
+            arg_types=[any_type, any_type],
+            arg_kinds=[ARG_STAR, ARG_STAR2],
+            arg_names=[None, None],
+            ret_type=any_type,
+            fallback=t.fallback,
+            is_ellipsis_args=True,
+            implicit=True,
+        )
+
+    def visit_overloaded(self, t: Overloaded) -> ProperType:
+        return t.fallback.accept(self)
+
+    def visit_tuple_type(self, t: TupleType) -> ProperType:
+        return t.partial_fallback.accept(self)
+
+    def visit_typeddict_type(self, t: TypedDictType) -> ProperType:
+        return t.fallback.accept(self)
+
+    def visit_literal_type(self, t: LiteralType) -> ProperType:
+        # The fallback for literal types should always be either
+        # something like int or str, or an enum class -- types that
+        # don't contain any TypeVars. So there's no need to visit it.
+        return t
+
+    def visit_union_type(self, t: UnionType) -> ProperType:
+        erased_items = [erase_type(item) for item in t.items]
+        from mypy.typeops import make_simplified_union
+
+        return make_simplified_union(erased_items)
+
+    def visit_type_type(self, t: TypeType) -> ProperType:
+        return TypeType.make_normalized(
+            t.item.accept(self), line=t.line, is_type_form=t.is_type_form
+        )
+
+    def visit_type_alias_type(self, t: TypeAliasType) -> ProperType:
+        raise RuntimeError("Type aliases should be expanded before accepting this visitor")
+
+
+def erase_typevars(t: Type, ids_to_erase: Container[TypeVarId] | None = None) -> Type:
+    """Replace all type variables in a type with any,
+    or just the ones in the provided collection.
+    """
+
+    if ids_to_erase is None:
+        return t.accept(TypeVarEraser(None, AnyType(TypeOfAny.special_form)))
+
+    def erase_id(id: TypeVarId) -> bool:
+        return id in ids_to_erase
+
+    return t.accept(TypeVarEraser(erase_id, AnyType(TypeOfAny.special_form)))
+
+
+def erase_meta_id(id: TypeVarId) -> bool:
+    return id.is_meta_var()
+
+
+def replace_meta_vars(t: Type, target_type: Type) -> Type:
+    """Replace unification variables in a type with the target type."""
+    return t.accept(TypeVarEraser(erase_meta_id, target_type))
+
+
+class TypeVarEraser(TypeTranslator):
+    """Implementation of type erasure"""
+
+    def __init__(self, erase_id: Callable[[TypeVarId], bool] | None, replacement: Type) -> None:
+        super().__init__()
+        self.erase_id = erase_id
+        self.replacement = replacement
+
+    def visit_type_var(self, t: TypeVarType) -> Type:
+        if self.erase_id is None or self.erase_id(t.id):
+            return self.replacement
+        return t
+
+    # TODO: below two methods duplicate some logic with expand_type().
+    # In fact, we may want to refactor this whole visitor to use expand_type().
+    def visit_instance(self, t: Instance) -> Type:
+        result = super().visit_instance(t)
+        assert isinstance(result, ProperType) and isinstance(result, Instance)
+        if t.type.fullname == "builtins.tuple":
+            # Normalize Tuple[*Tuple[X, ...], ...] -> Tuple[X, ...]
+            arg = result.args[0]
+            if isinstance(arg, UnpackType):
+                unpacked = get_proper_type(arg.type)
+                if isinstance(unpacked, Instance):
+                    assert unpacked.type.fullname == "builtins.tuple"
+                    return unpacked
+        return result
+
+    def visit_tuple_type(self, t: TupleType) -> Type:
+        result = super().visit_tuple_type(t)
+        assert isinstance(result, ProperType) and isinstance(result, TupleType)
+        if len(result.items) == 1:
+            # Normalize Tuple[*Tuple[X, ...]] -> Tuple[X, ...]
+            item = result.items[0]
+            if isinstance(item, UnpackType):
+                unpacked = get_proper_type(item.type)
+                if isinstance(unpacked, Instance):
+                    assert unpacked.type.fullname == "builtins.tuple"
+                    if result.partial_fallback.type.fullname != "builtins.tuple":
+                        # If it is a subtype (like named tuple) we need to preserve it,
+                        # this essentially mimics the logic in tuple_fallback().
+                        return result.partial_fallback.accept(self)
+                    return unpacked
+        return result
+
+    def visit_callable_type(self, t: CallableType) -> Type:
+        result = super().visit_callable_type(t)
+        assert isinstance(result, ProperType) and isinstance(result, CallableType)
+        # Usually this is done in semanal_typeargs.py, but erasure can create
+        # a non-normal callable from normal one.
+        result.normalize_trivial_unpack()
+        return result
+
+    def visit_type_var_tuple(self, t: TypeVarTupleType) -> Type:
+        if self.erase_id is None or self.erase_id(t.id):
+            return t.tuple_fallback.copy_modified(args=[self.replacement])
+        return t
+
+    def visit_param_spec(self, t: ParamSpecType) -> Type:
+        # TODO: we should probably preserve prefix here.
+        if self.erase_id is None or self.erase_id(t.id):
+            return self.replacement
+        return t
+
+    def visit_type_alias_type(self, t: TypeAliasType) -> Type:
+        # Type alias target can't contain bound type variables (not bound by the type
+        # alias itself), so it is safe to just erase the arguments.
+        return t.copy_modified(args=[a.accept(self) for a in t.args])
+
+
+def remove_instance_last_known_values(t: Type) -> Type:
+    return t.accept(LastKnownValueEraser())
+
+
+class LastKnownValueEraser(TypeTranslator):
+    """Removes the Literal[...] type that may be associated with any
+    Instance types."""
+
+    def visit_instance(self, t: Instance) -> Type:
+        if not t.last_known_value and not t.args:
+            return t
+        return t.copy_modified(args=[a.accept(self) for a in t.args], last_known_value=None)
+
+    def visit_type_alias_type(self, t: TypeAliasType) -> Type:
+        # Type aliases can't contain literal values, because they are
+        # always constructed as explicit types.
+        return t
+
+    def visit_union_type(self, t: UnionType) -> Type:
+        new = cast(UnionType, super().visit_union_type(t))
+        # Erasure can result in many duplicate items; merge them.
+        # Call make_simplified_union only on lists of instance types
+        # that all have the same fullname, to avoid simplifying too
+        # much.
+        instances = [item for item in new.items if isinstance(get_proper_type(item), Instance)]
+        # Avoid merge in simple cases such as optional types.
+        if len(instances) > 1:
+            instances_by_name: dict[str, list[Instance]] = {}
+            p_new_items = get_proper_types(new.items)
+            for p_item in p_new_items:
+                if isinstance(p_item, Instance) and not p_item.args:
+                    instances_by_name.setdefault(p_item.type.fullname, []).append(p_item)
+            merged: list[Type] = []
+            for item in new.items:
+                orig_item = item
+                item = get_proper_type(item)
+                if isinstance(item, Instance) and not item.args:
+                    types = instances_by_name.get(item.type.fullname)
+                    if types is not None:
+                        if len(types) == 1:
+                            merged.append(item)
+                        else:
+                            from mypy.typeops import make_simplified_union
+
+                            merged.append(make_simplified_union(types))
+                            del instances_by_name[item.type.fullname]
+                else:
+                    merged.append(orig_item)
+            return UnionType.make_union(merged)
+        return new
+
+
+def shallow_erase_type_for_equality(typ: Type) -> ProperType:
+    """Erase type variables from Instance's"""
+    p_typ = get_proper_type(typ)
+    if isinstance(p_typ, Instance):
+        if not p_typ.args:
+            return p_typ
+        args = erased_vars(p_typ.type.defn.type_vars, TypeOfAny.special_form)
+        return Instance(p_typ.type, args, p_typ.line)
+    if isinstance(p_typ, UnionType):
+        items = [shallow_erase_type_for_equality(item) for item in p_typ.items]
+        return UnionType.make_union(items)
+    return p_typ

venv/lib/python3.11/site-packages/mypy/error_formatter.py

@@ -0,0 +1,39 @@
+"""Defines the different custom formats in which mypy can output."""
+
+import json
+from abc import ABC, abstractmethod
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from mypy.errors import MypyError
+
+
+class ErrorFormatter(ABC):
+    """Base class to define how errors are formatted before being printed."""
+
+    @abstractmethod
+    def report_error(self, error: "MypyError") -> str:
+        raise NotImplementedError
+
+
+class JSONFormatter(ErrorFormatter):
+    """Formatter for basic JSON output format."""
+
+    def report_error(self, error: "MypyError") -> str:
+        """Prints out the errors as simple, static JSON lines."""
+        return json.dumps(
+            {
+                "file": error.file_path,
+                "line": error.line,
+                "column": error.column,
+                "end_line": error.end_line,
+                "end_column": error.end_column,
+                "message": error.message,
+                "hint": None if len(error.hints) == 0 else "\n".join(error.hints),
+                "code": error.errorcode,
+                "severity": error.severity,
+            }
+        )
+
+
+OUTPUT_CHOICES = {"json": JSONFormatter()}

venv/lib/python3.11/site-packages/mypy/errorcodes.py

@@ -0,0 +1,333 @@
+"""Classification of possible errors mypy can detect.
+
+These can be used for filtering specific errors.
+"""
+
+from __future__ import annotations
+
+from collections import defaultdict
+from typing import Final
+
+from mypy_extensions import mypyc_attr
+
+error_codes: dict[str, ErrorCode] = {}
+sub_code_map: dict[str, set[str]] = defaultdict(set)
+
+
+@mypyc_attr(allow_interpreted_subclasses=True)
+class ErrorCode:
+    def __init__(
+        self,
+        code: str,
+        description: str,
+        category: str,
+        default_enabled: bool = True,
+        sub_code_of: ErrorCode | None = None,
+    ) -> None:
+        self.code = code
+        self.description = description
+        self.category = category
+        self.default_enabled = default_enabled
+        self.sub_code_of = sub_code_of
+        if sub_code_of is not None:
+            assert sub_code_of.sub_code_of is None, "Nested subcategories are not supported"
+            sub_code_map[sub_code_of.code].add(code)
+        error_codes[code] = self
+
+    def __str__(self) -> str:
+        return f"<ErrorCode {self.code}>"
+
+    def __repr__(self) -> str:
+        """This doesn't fulfill the goals of repr but it's better than the default view."""
+        return f"<ErrorCode {self.category}: {self.code}>"
+
+    def __eq__(self, other: object) -> bool:
+        if not isinstance(other, ErrorCode):
+            return False
+        return self.code == other.code
+
+    def __hash__(self) -> int:
+        return hash((self.code,))
+
+
+ATTR_DEFINED: Final = ErrorCode("attr-defined", "Check that attribute exists", "General")
+NAME_DEFINED: Final = ErrorCode("name-defined", "Check that name is defined", "General")
+CALL_ARG: Final = ErrorCode(
+    "call-arg", "Check number, names and kinds of arguments in calls", "General"
+)
+ARG_TYPE: Final = ErrorCode("arg-type", "Check argument types in calls", "General")
+CALL_OVERLOAD: Final = ErrorCode(
+    "call-overload", "Check that an overload variant matches arguments", "General"
+)
+VALID_TYPE: Final = ErrorCode("valid-type", "Check that type (annotation) is valid", "General")
+NONETYPE_TYPE: Final = ErrorCode(
+    "nonetype-type", "Check that type (annotation) is not NoneType", "General"
+)
+VAR_ANNOTATED: Final = ErrorCode(
+    "var-annotated", "Require variable annotation if type can't be inferred", "General"
+)
+OVERRIDE: Final = ErrorCode(
+    "override", "Check that method override is compatible with base class", "General"
+)
+RETURN: Final = ErrorCode("return", "Check that function always returns a value", "General")
+RETURN_VALUE: Final = ErrorCode(
+    "return-value", "Check that return value is compatible with signature", "General"
+)
+ASSIGNMENT: Final = ErrorCode(
+    "assignment", "Check that assigned value is compatible with target", "General"
+)
+METHOD_ASSIGN: Final = ErrorCode(
+    "method-assign",
+    "Check that assignment target is not a method",
+    "General",
+    sub_code_of=ASSIGNMENT,
+)
+TYPE_ARG: Final = ErrorCode("type-arg", "Check that generic type arguments are present", "General")
+TYPE_VAR: Final = ErrorCode("type-var", "Check that type variable values are valid", "General")
+UNION_ATTR: Final = ErrorCode(
+    "union-attr", "Check that attribute exists in each item of a union", "General"
+)
+INDEX: Final = ErrorCode("index", "Check indexing operations", "General")
+OPERATOR: Final = ErrorCode("operator", "Check that operator is valid for operands", "General")
+LIST_ITEM: Final = ErrorCode(
+    "list-item", "Check list items in a list expression [item, ...]", "General"
+)
+DICT_ITEM: Final = ErrorCode(
+    "dict-item", "Check dict items in a dict expression {key: value, ...}", "General"
+)
+TYPEDDICT_ITEM: Final = ErrorCode(
+    "typeddict-item", "Check items when constructing TypedDict", "General"
+)
+TYPEDDICT_UNKNOWN_KEY: Final = ErrorCode(
+    "typeddict-unknown-key",
+    "Check unknown keys when constructing TypedDict",
+    "General",
+    sub_code_of=TYPEDDICT_ITEM,
+)
+HAS_TYPE: Final = ErrorCode(
+    "has-type", "Check that type of reference can be determined", "General"
+)
+IMPORT: Final = ErrorCode(
+    "import", "Require that imported module can be found or has stubs", "General"
+)
+IMPORT_NOT_FOUND: Final = ErrorCode(
+    "import-not-found", "Require that imported module can be found", "General", sub_code_of=IMPORT
+)
+IMPORT_UNTYPED: Final = ErrorCode(
+    "import-untyped", "Require that imported module has stubs", "General", sub_code_of=IMPORT
+)
+NO_REDEF: Final = ErrorCode("no-redef", "Check that each name is defined once", "General")
+FUNC_RETURNS_VALUE: Final = ErrorCode(
+    "func-returns-value", "Check that called function returns a value in value context", "General"
+)
+ABSTRACT: Final = ErrorCode(
+    "abstract", "Prevent instantiation of classes with abstract attributes", "General"
+)
+TYPE_ABSTRACT: Final = ErrorCode(
+    "type-abstract", "Require only concrete classes where Type[...] is expected", "General"
+)
+VALID_NEWTYPE: Final = ErrorCode(
+    "valid-newtype", "Check that argument 2 to NewType is valid", "General"
+)
+STRING_FORMATTING: Final = ErrorCode(
+    "str-format", "Check that string formatting/interpolation is type-safe", "General"
+)
+STR_BYTES_PY3: Final = ErrorCode(
+    "str-bytes-safe", "Warn about implicit coercions related to bytes and string types", "General"
+)
+EXIT_RETURN: Final = ErrorCode(
+    "exit-return", "Warn about too general return type for '__exit__'", "General"
+)
+LITERAL_REQ: Final = ErrorCode("literal-required", "Check that value is a literal", "General")
+UNUSED_COROUTINE: Final = ErrorCode(
+    "unused-coroutine", "Ensure that all coroutines are used", "General"
+)
+EMPTY_BODY: Final = ErrorCode(
+    "empty-body",
+    "A dedicated error code to opt out return errors for empty/trivial bodies",
+    "General",
+)
+SAFE_SUPER: Final = ErrorCode(
+    "safe-super", "Warn about calls to abstract methods with empty/trivial bodies", "General"
+)
+TOP_LEVEL_AWAIT: Final = ErrorCode(
+    "top-level-await", "Warn about top level await expressions", "General"
+)
+AWAIT_NOT_ASYNC: Final = ErrorCode(
+    "await-not-async", 'Warn about "await" outside coroutine ("async def")', "General"
+)
+# These error codes aren't enabled by default.
+NO_UNTYPED_DEF: Final = ErrorCode(
+    "no-untyped-def", "Check that every function has an annotation", "General"
+)
+NO_UNTYPED_CALL: Final = ErrorCode(
+    "no-untyped-call",
+    "Disallow calling functions without type annotations from annotated functions",
+    "General",
+)
+REDUNDANT_CAST: Final = ErrorCode(
+    "redundant-cast", "Check that cast changes type of expression", "General"
+)
+ASSERT_TYPE: Final = ErrorCode("assert-type", "Check that assert_type() call succeeds", "General")
+COMPARISON_OVERLAP: Final = ErrorCode(
+    "comparison-overlap", "Check that types in comparisons and 'in' expressions overlap", "General"
+)
+NO_ANY_UNIMPORTED: Final = ErrorCode(
+    "no-any-unimported", 'Reject "Any" types from unfollowed imports', "General"
+)
+NO_ANY_RETURN: Final = ErrorCode(
+    "no-any-return",
+    'Reject returning value with "Any" type if return type is not "Any"',
+    "General",
+)
+UNREACHABLE: Final = ErrorCode(
+    "unreachable", "Warn about unreachable statements or expressions", "General"
+)
+ANNOTATION_UNCHECKED: Final = ErrorCode(
+    "annotation-unchecked", "Notify about type annotations in unchecked functions", "General"
+)
+TYPEDDICT_READONLY_MUTATED: Final = ErrorCode(
+    "typeddict-readonly-mutated", "TypedDict's ReadOnly key is mutated", "General"
+)
+POSSIBLY_UNDEFINED: Final = ErrorCode(
+    "possibly-undefined",
+    "Warn about variables that are defined only in some execution paths",
+    "General",
+    default_enabled=False,
+)
+REDUNDANT_EXPR: Final = ErrorCode(
+    "redundant-expr", "Warn about redundant expressions", "General", default_enabled=False
+)
+TRUTHY_BOOL: Final = ErrorCode(
+    "truthy-bool",
+    "Warn about expressions that could always evaluate to true in boolean contexts",
+    "General",
+    default_enabled=False,
+)
+TRUTHY_FUNCTION: Final = ErrorCode(
+    "truthy-function",
+    "Warn about function that always evaluate to true in boolean contexts",
+    "General",
+)
+TRUTHY_ITERABLE: Final = ErrorCode(
+    "truthy-iterable",
+    "Warn about Iterable expressions that could always evaluate to true in boolean contexts",
+    "General",
+    default_enabled=False,
+)
+STR_UNPACK: Final[ErrorCode] = ErrorCode(
+    "str-unpack", "Warn about expressions that unpack str", "General"
+)
+NAME_MATCH: Final = ErrorCode(
+    "name-match", "Check that type definition has consistent naming", "General"
+)
+NO_OVERLOAD_IMPL: Final = ErrorCode(
+    "no-overload-impl",
+    "Check that overloaded functions outside stub files have an implementation",
+    "General",
+)
+IGNORE_WITHOUT_CODE: Final = ErrorCode(
+    "ignore-without-code",
+    "Warn about '# type: ignore' comments which do not have error codes",
+    "General",
+    default_enabled=False,
+)
+UNUSED_AWAITABLE: Final = ErrorCode(
+    "unused-awaitable",
+    "Ensure that all awaitable values are used",
+    "General",
+    default_enabled=False,
+)
+REDUNDANT_SELF_TYPE: Final = ErrorCode(
+    "redundant-self",
+    "Warn about redundant Self type annotations on method first argument",
+    "General",
+    default_enabled=False,
+)
+USED_BEFORE_DEF: Final = ErrorCode(
+    "used-before-def", "Warn about variables that are used before they are defined", "General"
+)
+UNUSED_IGNORE: Final = ErrorCode(
+    "unused-ignore", "Ensure that all type ignores are used", "General", default_enabled=False
+)
+EXPLICIT_OVERRIDE_REQUIRED: Final = ErrorCode(
+    "explicit-override",
+    "Require @override decorator if method is overriding a base class method",
+    "General",
+    default_enabled=False,
+)
+UNIMPORTED_REVEAL: Final = ErrorCode(
+    "unimported-reveal",
+    "Require explicit import from typing or typing_extensions for reveal_type",
+    "General",
+    default_enabled=False,
+)
+MUTABLE_OVERRIDE: Final = ErrorCode(
+    "mutable-override",
+    "Reject covariant overrides for mutable attributes",
+    "General",
+    default_enabled=False,
+)
+EXHAUSTIVE_MATCH: Final = ErrorCode(
+    "exhaustive-match",
+    "Reject match statements that are not exhaustive",
+    "General",
+    default_enabled=False,
+)
+METACLASS: Final = ErrorCode("metaclass", "Ensure that metaclass is valid", "General")
+MAYBE_UNRECOGNIZED_STR_TYPEFORM: Final = ErrorCode(
+    "maybe-unrecognized-str-typeform",
+    "Error when a string is used where a TypeForm is expected but a string annotation cannot be recognized",
+    "General",
+)
+
+# Syntax errors are often blocking.
+SYNTAX: Final = ErrorCode("syntax", "Report syntax errors", "General")
+
+# This is a catch-all for remaining uncategorized errors.
+MISC: Final = ErrorCode("misc", "Miscellaneous other checks", "General")
+
+OVERLOAD_CANNOT_MATCH: Final = ErrorCode(
+    "overload-cannot-match",
+    "Warn if an @overload signature can never be matched",
+    "General",
+    sub_code_of=MISC,
+)
+
+OVERLOAD_OVERLAP: Final = ErrorCode(
+    "overload-overlap",
+    "Warn if multiple @overload variants overlap in unsafe ways",
+    "General",
+    sub_code_of=MISC,
+)
+
+PROPERTY_DECORATOR: Final = ErrorCode(
+    "prop-decorator",
+    "Decorators on top of @property are not supported",
+    "General",
+    sub_code_of=MISC,
+)
+
+UNTYPED_DECORATOR: Final = ErrorCode(
+    "untyped-decorator", "Error if an untyped decorator makes a typed function untyped", "General"
+)
+
+NARROWED_TYPE_NOT_SUBTYPE: Final = ErrorCode(
+    "narrowed-type-not-subtype",
+    "Warn if a TypeIs function's narrowed type is not a subtype of the original type",
+    "General",
+)
+
+EXPLICIT_ANY: Final = ErrorCode(
+    "explicit-any", "Warn about explicit Any type annotations", "General"
+)
+
+DEPRECATED: Final = ErrorCode(
+    "deprecated",
+    "Warn when importing or using deprecated (overloaded) functions, methods or classes",
+    "General",
+    default_enabled=False,
+)
+
+# This copy will not include any error codes defined later in the plugins.
+mypy_error_codes = error_codes.copy()

venv/lib/python3.11/site-packages/mypy/evalexpr.py

@@ -0,0 +1,211 @@
+"""
+
+Evaluate an expression.
+
+Used by stubtest; in a separate file because things break if we don't
+put it in a mypyc-compiled file.
+
+"""
+
+import ast
+from typing import Final
+
+import mypy.nodes
+from mypy.visitor import ExpressionVisitor
+
+UNKNOWN = object()
+
+
+class _NodeEvaluator(ExpressionVisitor[object]):
+    def visit_int_expr(self, o: mypy.nodes.IntExpr) -> int:
+        return o.value
+
+    def visit_str_expr(self, o: mypy.nodes.StrExpr) -> str:
+        return o.value
+
+    def visit_bytes_expr(self, o: mypy.nodes.BytesExpr) -> object:
+        # The value of a BytesExpr is a string created from the repr()
+        # of the bytes object. Get the original bytes back.
+        try:
+            return ast.literal_eval(f"b'{o.value}'")
+        except SyntaxError:
+            return ast.literal_eval(f'b"{o.value}"')
+
+    def visit_float_expr(self, o: mypy.nodes.FloatExpr) -> float:
+        return o.value
+
+    def visit_complex_expr(self, o: mypy.nodes.ComplexExpr) -> object:
+        return o.value
+
+    def visit_ellipsis(self, o: mypy.nodes.EllipsisExpr) -> object:
+        return Ellipsis
+
+    def visit_star_expr(self, o: mypy.nodes.StarExpr) -> object:
+        return UNKNOWN
+
+    def visit_name_expr(self, o: mypy.nodes.NameExpr) -> object:
+        if o.name == "True":
+            return True
+        elif o.name == "False":
+            return False
+        elif o.name == "None":
+            return None
+        # TODO: Handle more names by figuring out a way to hook into the
+        # symbol table.
+        return UNKNOWN
+
+    def visit_member_expr(self, o: mypy.nodes.MemberExpr) -> object:
+        return UNKNOWN
+
+    def visit_yield_from_expr(self, o: mypy.nodes.YieldFromExpr) -> object:
+        return UNKNOWN
+
+    def visit_yield_expr(self, o: mypy.nodes.YieldExpr) -> object:
+        return UNKNOWN
+
+    def visit_call_expr(self, o: mypy.nodes.CallExpr) -> object:
+        return UNKNOWN
+
+    def visit_op_expr(self, o: mypy.nodes.OpExpr) -> object:
+        return UNKNOWN
+
+    def visit_comparison_expr(self, o: mypy.nodes.ComparisonExpr) -> object:
+        return UNKNOWN
+
+    def visit_cast_expr(self, o: mypy.nodes.CastExpr) -> object:
+        return o.expr.accept(self)
+
+    def visit_type_form_expr(self, o: mypy.nodes.TypeFormExpr) -> object:
+        return UNKNOWN
+
+    def visit_assert_type_expr(self, o: mypy.nodes.AssertTypeExpr) -> object:
+        return o.expr.accept(self)
+
+    def visit_reveal_expr(self, o: mypy.nodes.RevealExpr) -> object:
+        return UNKNOWN
+
+    def visit_super_expr(self, o: mypy.nodes.SuperExpr) -> object:
+        return UNKNOWN
+
+    def visit_unary_expr(self, o: mypy.nodes.UnaryExpr) -> object:
+        operand = o.expr.accept(self)
+        if operand is UNKNOWN:
+            return UNKNOWN
+        if o.op == "-":
+            if isinstance(operand, (int, float, complex)):
+                return -operand
+        elif o.op == "+":
+            if isinstance(operand, (int, float, complex)):
+                return +operand
+        elif o.op == "~":
+            if isinstance(operand, int):
+                return ~operand
+        elif o.op == "not":
+            if isinstance(operand, (bool, int, float, str, bytes)):
+                return not operand
+        return UNKNOWN
+
+    def visit_assignment_expr(self, o: mypy.nodes.AssignmentExpr) -> object:
+        return o.value.accept(self)
+
+    def visit_list_expr(self, o: mypy.nodes.ListExpr) -> object:
+        items = [item.accept(self) for item in o.items]
+        if all(item is not UNKNOWN for item in items):
+            return items
+        return UNKNOWN
+
+    def visit_dict_expr(self, o: mypy.nodes.DictExpr) -> object:
+        items = [
+            (UNKNOWN if key is None else key.accept(self), value.accept(self))
+            for key, value in o.items
+        ]
+        if all(key is not UNKNOWN and value is not None for key, value in items):
+            return dict(items)
+        return UNKNOWN
+
+    def visit_tuple_expr(self, o: mypy.nodes.TupleExpr) -> object:
+        items = [item.accept(self) for item in o.items]
+        if all(item is not UNKNOWN for item in items):
+            return tuple(items)
+        return UNKNOWN
+
+    def visit_set_expr(self, o: mypy.nodes.SetExpr) -> object:
+        items = [item.accept(self) for item in o.items]
+        if all(item is not UNKNOWN for item in items):
+            return set(items)
+        return UNKNOWN
+
+    def visit_index_expr(self, o: mypy.nodes.IndexExpr) -> object:
+        return UNKNOWN
+
+    def visit_type_application(self, o: mypy.nodes.TypeApplication) -> object:
+        return UNKNOWN
+
+    def visit_lambda_expr(self, o: mypy.nodes.LambdaExpr) -> object:
+        return UNKNOWN
+
+    def visit_list_comprehension(self, o: mypy.nodes.ListComprehension) -> object:
+        return UNKNOWN
+
+    def visit_set_comprehension(self, o: mypy.nodes.SetComprehension) -> object:
+        return UNKNOWN
+
+    def visit_dictionary_comprehension(self, o: mypy.nodes.DictionaryComprehension) -> object:
+        return UNKNOWN
+
+    def visit_generator_expr(self, o: mypy.nodes.GeneratorExpr) -> object:
+        return UNKNOWN
+
+    def visit_slice_expr(self, o: mypy.nodes.SliceExpr) -> object:
+        return UNKNOWN
+
+    def visit_conditional_expr(self, o: mypy.nodes.ConditionalExpr) -> object:
+        return UNKNOWN
+
+    def visit_type_var_expr(self, o: mypy.nodes.TypeVarExpr) -> object:
+        return UNKNOWN
+
+    def visit_paramspec_expr(self, o: mypy.nodes.ParamSpecExpr) -> object:
+        return UNKNOWN
+
+    def visit_type_var_tuple_expr(self, o: mypy.nodes.TypeVarTupleExpr) -> object:
+        return UNKNOWN
+
+    def visit_type_alias_expr(self, o: mypy.nodes.TypeAliasExpr) -> object:
+        return UNKNOWN
+
+    def visit_namedtuple_expr(self, o: mypy.nodes.NamedTupleExpr) -> object:
+        return UNKNOWN
+
+    def visit_enum_call_expr(self, o: mypy.nodes.EnumCallExpr) -> object:
+        return UNKNOWN
+
+    def visit_typeddict_expr(self, o: mypy.nodes.TypedDictExpr) -> object:
+        return UNKNOWN
+
+    def visit_newtype_expr(self, o: mypy.nodes.NewTypeExpr) -> object:
+        return UNKNOWN
+
+    def visit__promote_expr(self, o: mypy.nodes.PromoteExpr) -> object:
+        return UNKNOWN
+
+    def visit_await_expr(self, o: mypy.nodes.AwaitExpr) -> object:
+        return UNKNOWN
+
+    def visit_template_str_expr(self, o: mypy.nodes.TemplateStrExpr) -> object:
+        return UNKNOWN
+
+    def visit_temp_node(self, o: mypy.nodes.TempNode) -> object:
+        return UNKNOWN
+
+
+_evaluator: Final = _NodeEvaluator()
+
+
+def evaluate_expression(expr: mypy.nodes.Expression) -> object:
+    """Evaluate an expression at runtime.
+
+    Return the result of the expression, or UNKNOWN if the expression cannot be
+    evaluated.
+    """
+    return expr.accept(_evaluator)

venv/lib/python3.11/site-packages/mypy/expandtype.py

@@ -0,0 +1,662 @@
+from __future__ import annotations
+
+from collections.abc import Iterable, Mapping
+from typing import Final, TypeVar, cast, overload
+
+from mypy.nodes import ARG_STAR, ArgKind, FakeInfo, Var
+from mypy.state import state
+from mypy.types import (
+    ANY_STRATEGY,
+    AnyType,
+    BoolTypeQuery,
+    CallableType,
+    DeletedType,
+    ErasedType,
+    FunctionLike,
+    Instance,
+    LiteralType,
+    NoneType,
+    Overloaded,
+    Parameters,
+    ParamSpecFlavor,
+    ParamSpecType,
+    PartialType,
+    ProperType,
+    TrivialSyntheticTypeTranslator,
+    TupleType,
+    Type,
+    TypeAliasType,
+    TypedDictType,
+    TypeOfAny,
+    TypeType,
+    TypeVarId,
+    TypeVarLikeType,
+    TypeVarTupleType,
+    TypeVarType,
+    UnboundType,
+    UninhabitedType,
+    UnionType,
+    UnpackType,
+    flatten_nested_unions,
+    get_proper_type,
+    split_with_prefix_and_suffix,
+)
+from mypy.typevartuples import split_with_instance
+
+# Solving the import cycle:
+import mypy.type_visitor  # ruff: isort: skip
+
+# WARNING: these functions should never (directly or indirectly) depend on
+# is_subtype(), meet_types(), join_types() etc.
+# TODO: add a static dependency test for this.
+
+
+@overload
+def expand_type(typ: CallableType, env: Mapping[TypeVarId, Type]) -> CallableType: ...
+
+
+@overload
+def expand_type(typ: ProperType, env: Mapping[TypeVarId, Type]) -> ProperType: ...
+
+
+@overload
+def expand_type(typ: Type, env: Mapping[TypeVarId, Type]) -> Type: ...
+
+
+def expand_type(typ: Type, env: Mapping[TypeVarId, Type]) -> Type:
+    """Substitute any type variable references in a type given by a type
+    environment.
+    """
+    return typ.accept(ExpandTypeVisitor(env))
+
+
+@overload
+def expand_type_by_instance(typ: CallableType, instance: Instance) -> CallableType: ...
+
+
+@overload
+def expand_type_by_instance(typ: ProperType, instance: Instance) -> ProperType: ...
+
+
+@overload
+def expand_type_by_instance(typ: Type, instance: Instance) -> Type: ...
+
+
+def expand_type_by_instance(typ: Type, instance: Instance) -> Type:
+    """Substitute type variables in type using values from an Instance.
+    Type variables are considered to be bound by the class declaration."""
+    if not instance.args and not instance.type.has_type_var_tuple_type:
+        return typ
+    else:
+        variables: dict[TypeVarId, Type] = {}
+        if instance.type.has_type_var_tuple_type:
+            assert instance.type.type_var_tuple_prefix is not None
+            assert instance.type.type_var_tuple_suffix is not None
+
+            args_prefix, args_middle, args_suffix = split_with_instance(instance)
+            tvars_prefix, tvars_middle, tvars_suffix = split_with_prefix_and_suffix(
+                tuple(instance.type.defn.type_vars),
+                instance.type.type_var_tuple_prefix,
+                instance.type.type_var_tuple_suffix,
+            )
+            tvar = tvars_middle[0]
+            assert isinstance(tvar, TypeVarTupleType)
+            variables = {tvar.id: TupleType(list(args_middle), tvar.tuple_fallback)}
+            instance_args = args_prefix + args_suffix
+            tvars = tvars_prefix + tvars_suffix
+        else:
+            tvars = tuple(instance.type.defn.type_vars)
+            instance_args = instance.args
+
+        for binder, arg in zip(tvars, instance_args):
+            assert isinstance(binder, TypeVarLikeType)
+            variables[binder.id] = arg
+
+        return expand_type(typ, variables)
+
+
+F = TypeVar("F", bound=FunctionLike)
+
+
+def freshen_function_type_vars(callee: F) -> F:
+    """Substitute fresh type variables for generic function type variables."""
+    if isinstance(callee, CallableType):
+        if not callee.is_generic():
+            return callee
+        tvs = []
+        tvmap: dict[TypeVarId, Type] = {}
+        for v in callee.variables:
+            tv = v.new_unification_variable(v)
+            tvs.append(tv)
+            tvmap[v.id] = tv
+        fresh = expand_type(callee, tvmap).copy_modified(variables=tvs)
+        return cast(F, fresh)
+    else:
+        assert isinstance(callee, Overloaded)
+        fresh_overload = Overloaded([freshen_function_type_vars(item) for item in callee.items])
+        return cast(F, fresh_overload)
+
+
+class HasGenericCallable(BoolTypeQuery):
+    def __init__(self) -> None:
+        super().__init__(ANY_STRATEGY)
+
+    def visit_callable_type(self, t: CallableType) -> bool:
+        return t.is_generic() or super().visit_callable_type(t)
+
+
+# Share a singleton since this is performance sensitive
+has_generic_callable: Final = HasGenericCallable()
+
+
+T = TypeVar("T", bound=Type)
+
+
+def freshen_all_functions_type_vars(t: T) -> T:
+    result: Type
+    has_generic_callable.reset()
+    if not t.accept(has_generic_callable):
+        return t  # Fast path to avoid expensive freshening
+    else:
+        result = t.accept(FreshenCallableVisitor())
+        assert isinstance(result, type(t))
+        return result
+
+
+class FreshenCallableVisitor(mypy.type_visitor.TypeTranslator):
+    def visit_callable_type(self, t: CallableType) -> Type:
+        result = super().visit_callable_type(t)
+        assert isinstance(result, ProperType) and isinstance(result, CallableType)
+        return freshen_function_type_vars(result)
+
+    def visit_type_alias_type(self, t: TypeAliasType) -> Type:
+        # Same as for ExpandTypeVisitor
+        return t.copy_modified(args=[arg.accept(self) for arg in t.args])
+
+
+class ExpandTypeVisitor(TrivialSyntheticTypeTranslator):
+    """Visitor that substitutes type variables with values."""
+
+    variables: Mapping[TypeVarId, Type]  # TypeVar id -> TypeVar value
+
+    def __init__(self, variables: Mapping[TypeVarId, Type]) -> None:
+        super().__init__()
+        self.variables = variables
+        self.recursive_tvar_guard: dict[TypeVarId, Type | None] | None = None
+
+    def visit_unbound_type(self, t: UnboundType) -> Type:
+        return t
+
+    def visit_any(self, t: AnyType) -> Type:
+        return t
+
+    def visit_none_type(self, t: NoneType) -> Type:
+        return t
+
+    def visit_uninhabited_type(self, t: UninhabitedType) -> Type:
+        return t
+
+    def visit_deleted_type(self, t: DeletedType) -> Type:
+        return t
+
+    def visit_erased_type(self, t: ErasedType) -> Type:
+        # This may happen during type inference if some function argument
+        # type is a generic callable, and its erased form will appear in inferred
+        # constraints, then solver may check subtyping between them, which will trigger
+        # unify_generic_callables(), this is why we can get here. Another example is
+        # when inferring type of lambda in generic context, the lambda body contains
+        # a generic method in generic class.
+        return t
+
+    def visit_instance(self, t: Instance) -> Type:
+        if len(t.args) == 0:
+            return t
+
+        args = self.expand_type_tuple_with_unpack(t.args)
+
+        if isinstance(t.type, FakeInfo):
+            # The type checker expands function definitions and bodies
+            # if they depend on constrained type variables but the body
+            # might contain a tuple type comment (e.g., # type: (int, float)),
+            # in which case 't.type' is not yet available.
+            #
+            # See: https://github.com/python/mypy/issues/16649
+            return t.copy_modified(args=args)
+
+        if t.type.fullname == "builtins.tuple":
+            # Normalize Tuple[*Tuple[X, ...], ...] -> Tuple[X, ...]
+            arg = args[0]
+            if isinstance(arg, UnpackType):
+                unpacked = get_proper_type(arg.type)
+                if isinstance(unpacked, Instance):
+                    # TODO: this and similar asserts below may be unsafe because get_proper_type()
+                    # may be called during semantic analysis before all invalid types are removed.
+                    assert unpacked.type.fullname == "builtins.tuple"
+                    args = list(unpacked.args)
+        return t.copy_modified(args=args)
+
+    def visit_type_var(self, t: TypeVarType) -> Type:
+        # Normally upper bounds can't contain other type variables, the only exception is
+        # special type variable Self`0 <: C[T, S], where C is the class where Self is used.
+        if t.id.is_self():
+            t = t.copy_modified(upper_bound=t.upper_bound.accept(self))
+        repl = self.variables.get(t.id, t)
+        if isinstance(repl, ProperType) and isinstance(repl, Instance):
+            # TODO: do we really need to do this?
+            # If I try to remove this special-casing ~40 tests fail on reveal_type().
+            return repl.copy_modified(last_known_value=None)
+        if isinstance(repl, TypeVarType) and repl.has_default():
+            if self.recursive_tvar_guard is None:
+                self.recursive_tvar_guard = {}
+            if (tvar_id := repl.id) in self.recursive_tvar_guard:
+                return self.recursive_tvar_guard[tvar_id] or repl
+            self.recursive_tvar_guard[tvar_id] = None
+            repl.default = repl.default.accept(self)
+            expanded = repl.accept(self)  # Note: `expanded is repl` may be true.
+            repl = repl if isinstance(expanded, TypeVarType) else expanded
+            self.recursive_tvar_guard[tvar_id] = repl
+        return repl
+
+    def visit_param_spec(self, t: ParamSpecType) -> Type:
+        # Set prefix to something empty, so we don't duplicate it below.
+        repl = self.variables.get(t.id, t.copy_modified(prefix=Parameters([], [], [])))
+        if isinstance(repl, ParamSpecType):
+            return repl.copy_modified(
+                flavor=t.flavor,
+                prefix=t.prefix.copy_modified(
+                    arg_types=self.expand_types(t.prefix.arg_types) + repl.prefix.arg_types,
+                    arg_kinds=t.prefix.arg_kinds + repl.prefix.arg_kinds,
+                    arg_names=t.prefix.arg_names + repl.prefix.arg_names,
+                ),
+            )
+        elif isinstance(repl, Parameters):
+            assert isinstance(t.upper_bound, ProperType) and isinstance(t.upper_bound, Instance)
+            if t.flavor == ParamSpecFlavor.BARE:
+                return Parameters(
+                    self.expand_types(t.prefix.arg_types) + repl.arg_types,
+                    t.prefix.arg_kinds + repl.arg_kinds,
+                    t.prefix.arg_names + repl.arg_names,
+                    variables=[*t.prefix.variables, *repl.variables],
+                    imprecise_arg_kinds=repl.imprecise_arg_kinds,
+                )
+            elif t.flavor == ParamSpecFlavor.ARGS:
+                assert all(k.is_positional() for k in t.prefix.arg_kinds)
+                return self._possible_callable_varargs(
+                    repl, list(t.prefix.arg_types), t.upper_bound
+                )
+            else:
+                assert t.flavor == ParamSpecFlavor.KWARGS
+                return self._possible_callable_kwargs(repl, t.upper_bound)
+        else:
+            # We could encode Any as trivial parameters etc., but it would be too verbose.
+            # TODO: assert this is a trivial type, like Any, Never, or object.
+            return repl
+
+    @classmethod
+    def _possible_callable_varargs(
+        cls, repl: Parameters, required_prefix: list[Type], tuple_type: Instance
+    ) -> ProperType:
+        """Given a callable, extract all parameters that can be passed as `*args`.
+
+        This builds a union of all (possibly variadic) tuples representing all possible
+        argument sequences that can be passed positionally. Each such tuple starts with
+        all required (pos-only without a default) arguments, followed by some prefix
+        of other arguments that can be passed positionally.
+        """
+        required_posargs = required_prefix
+        if repl.variables:
+            # We will tear the callable apart, do not leak type variables
+            return tuple_type
+        optional_posargs: list[Type] = []
+        for kind, name, type in zip(repl.arg_kinds, repl.arg_names, repl.arg_types):
+            if kind == ArgKind.ARG_POS and name is None:
+                if optional_posargs:
+                    # May happen following Unpack expansion without kinds correction
+                    required_posargs += optional_posargs
+                    optional_posargs = []
+                required_posargs.append(type)
+            elif kind.is_positional():
+                optional_posargs.append(type)
+            elif kind == ArgKind.ARG_STAR:
+                if isinstance(type, UnpackType):
+                    optional_posargs.append(type)
+                else:
+                    optional_posargs.append(UnpackType(Instance(tuple_type.type, [type])))
+                break
+        return UnionType.make_union(
+            [
+                TupleType(required_posargs + optional_posargs[:i], fallback=tuple_type)
+                for i in range(len(optional_posargs) + 1)
+            ]
+        )
+
+    @classmethod
+    def _possible_callable_kwargs(cls, repl: Parameters, dict_type: Instance) -> ProperType:
+        """Given a callable, extract all parameters that can be passed as `**kwargs`.
+
+        If the function only accepts **kwargs, this will be a `dict[str, KwargsValueType]`.
+        Otherwise, this will be a `TypedDict` containing all explicit args and ignoring
+        `**kwargs` (until PEP 728 `extra_items` is supported). TypedDict entries will
+        be required iff the corresponding argument is kw-only and has no default.
+        """
+        if repl.variables:
+            # We will tear the callable apart, do not leak type variables
+            return dict_type
+        kwargs = {}
+        required_names = set()
+        extra_items: Type = UninhabitedType()
+        for kind, name, type in zip(repl.arg_kinds, repl.arg_names, repl.arg_types):
+            if kind == ArgKind.ARG_NAMED and name is not None:
+                kwargs[name] = type
+                required_names.add(name)
+            elif kind == ArgKind.ARG_STAR2:
+                # Unpack[TypedDict] is normalized early, it isn't stored as Unpack
+                extra_items = type
+            elif not kind.is_star() and name is not None:
+                kwargs[name] = type
+        if not kwargs:
+            return Instance(dict_type.type, [dict_type.args[0], extra_items])
+        # TODO: when PEP 728 is implemented, pass extra_items below.
+        return TypedDictType(kwargs, required_names, set(), fallback=dict_type)
+
+    def visit_type_var_tuple(self, t: TypeVarTupleType) -> Type:
+        # Sometimes solver may need to expand a type variable with (a copy of) itself
+        # (usually together with other TypeVars, but it is hard to filter out TypeVarTuples).
+        repl = self.variables.get(t.id, t)
+        if isinstance(repl, TypeVarTupleType):
+            return repl
+        elif isinstance(repl, ProperType) and isinstance(repl, (AnyType, UninhabitedType)):
+            # Some failed inference scenarios will try to set all type variables to Never.
+            # Instead of being picky and require all the callers to wrap them,
+            # do this here instead.
+            # Note: most cases when this happens are handled in expand unpack below, but
+            # in rare cases (e.g. ParamSpec containing Unpack star args) it may be skipped.
+            return t.tuple_fallback.copy_modified(args=[repl])
+        raise NotImplementedError
+
+    def visit_unpack_type(self, t: UnpackType) -> Type:
+        # It is impossible to reasonably implement visit_unpack_type, because
+        # unpacking inherently expands to something more like a list of types.
+        #
+        # Relevant sections that can call unpack should call expand_unpack()
+        # instead.
+        # However, if the item is a variadic tuple, we can simply carry it over.
+        # In particular, if we expand A[*tuple[T, ...]] with substitutions {T: str},
+        # it is hard to assert this without getting proper type. Another important
+        # example is non-normalized types when called from semanal.py.
+        return UnpackType(t.type.accept(self))
+
+    def expand_unpack(self, t: UnpackType) -> list[Type]:
+        assert isinstance(t.type, TypeVarTupleType)
+        repl = get_proper_type(self.variables.get(t.type.id, t.type))
+        if isinstance(repl, UnpackType):
+            repl = get_proper_type(repl.type)
+        if isinstance(repl, TupleType):
+            return repl.items
+        elif (
+            isinstance(repl, Instance)
+            and repl.type.fullname == "builtins.tuple"
+            or isinstance(repl, TypeVarTupleType)
+        ):
+            return [UnpackType(typ=repl)]
+        elif isinstance(repl, (AnyType, UninhabitedType)):
+            # Replace *Ts = Any with *Ts = *tuple[Any, ...] and same for Never.
+            # These types may appear here as a result of user error or failed inference.
+            return [UnpackType(t.type.tuple_fallback.copy_modified(args=[repl]))]
+        else:
+            raise RuntimeError(f"Invalid type replacement to expand: {repl}")
+
+    def visit_parameters(self, t: Parameters) -> Type:
+        return t.copy_modified(arg_types=self.expand_types(t.arg_types))
+
+    def interpolate_args_for_unpack(self, t: CallableType, var_arg: UnpackType) -> list[Type]:
+        star_index = t.arg_kinds.index(ARG_STAR)
+        prefix = self.expand_types(t.arg_types[:star_index])
+        suffix = self.expand_types(t.arg_types[star_index + 1 :])
+
+        var_arg_type = get_proper_type(var_arg.type)
+        new_unpack: Type
+        if isinstance(var_arg_type, TupleType):
+            # We have something like Unpack[Tuple[Unpack[Ts], X1, X2]]
+            expanded_tuple = var_arg_type.accept(self)
+            assert isinstance(expanded_tuple, ProperType) and isinstance(expanded_tuple, TupleType)
+            expanded_items = expanded_tuple.items
+            fallback = var_arg_type.partial_fallback
+            new_unpack = UnpackType(TupleType(expanded_items, fallback))
+        elif isinstance(var_arg_type, TypeVarTupleType):
+            # We have plain Unpack[Ts]
+            fallback = var_arg_type.tuple_fallback
+            expanded_items = self.expand_unpack(var_arg)
+            new_unpack = UnpackType(TupleType(expanded_items, fallback))
+        # Since get_proper_type() may be called in semanal.py before callable
+        # normalization happens, we need to also handle non-normal cases here.
+        elif isinstance(var_arg_type, Instance):
+            # we have something like Unpack[Tuple[Any, ...]]
+            new_unpack = UnpackType(var_arg.type.accept(self))
+        else:
+            # We have invalid type in Unpack. This can happen when expanding aliases
+            # to Callable[[*Invalid], Ret]
+            new_unpack = AnyType(TypeOfAny.from_error, line=var_arg.line, column=var_arg.column)
+        return prefix + [new_unpack] + suffix
+
+    def visit_callable_type(self, t: CallableType) -> CallableType:
+        param_spec = t.param_spec()
+        if param_spec is not None:
+            repl = self.variables.get(param_spec.id)
+            # If a ParamSpec in a callable type is substituted with a
+            # callable type, we can't use normal substitution logic,
+            # since ParamSpec is actually split into two components
+            # *P.args and **P.kwargs in the original type. Instead, we
+            # must expand both of them with all the argument types,
+            # kinds and names in the replacement. The return type in
+            # the replacement is ignored.
+            if isinstance(repl, Parameters):
+                # We need to expand both the types in the prefix and the ParamSpec itself
+                expanded = t.copy_modified(
+                    arg_types=self.expand_types(t.arg_types[:-2]) + repl.arg_types,
+                    arg_kinds=t.arg_kinds[:-2] + repl.arg_kinds,
+                    arg_names=t.arg_names[:-2] + repl.arg_names,
+                    ret_type=t.ret_type.accept(self),
+                    type_guard=(t.type_guard.accept(self) if t.type_guard is not None else None),
+                    type_is=(t.type_is.accept(self) if t.type_is is not None else None),
+                    imprecise_arg_kinds=(t.imprecise_arg_kinds or repl.imprecise_arg_kinds),
+                    variables=[*repl.variables, *t.variables],
+                )
+                var_arg = expanded.var_arg()
+                if var_arg is not None and isinstance(var_arg.typ, UnpackType):
+                    # Sometimes we get new unpacks after expanding ParamSpec.
+                    expanded.normalize_trivial_unpack()
+                return expanded
+            elif isinstance(repl, ParamSpecType):
+                # We're substituting one ParamSpec for another; this can mean that the prefix
+                # changes, e.g. substitute Concatenate[int, P] in place of Q.
+                prefix = repl.prefix
+                clean_repl = repl.copy_modified(prefix=Parameters([], [], []))
+                return t.copy_modified(
+                    arg_types=self.expand_types(t.arg_types[:-2])
+                    + prefix.arg_types
+                    + [
+                        clean_repl.with_flavor(ParamSpecFlavor.ARGS),
+                        clean_repl.with_flavor(ParamSpecFlavor.KWARGS),
+                    ],
+                    arg_kinds=t.arg_kinds[:-2] + prefix.arg_kinds + t.arg_kinds[-2:],
+                    arg_names=t.arg_names[:-2] + prefix.arg_names + t.arg_names[-2:],
+                    ret_type=t.ret_type.accept(self),
+                    from_concatenate=t.from_concatenate or bool(repl.prefix.arg_types),
+                    imprecise_arg_kinds=(t.imprecise_arg_kinds or prefix.imprecise_arg_kinds),
+                )
+
+        var_arg = t.var_arg()
+        needs_normalization = False
+        if var_arg is not None and isinstance(var_arg.typ, UnpackType):
+            needs_normalization = True
+            arg_types = self.interpolate_args_for_unpack(t, var_arg.typ)
+        else:
+            arg_types = self.expand_types(t.arg_types)
+        expanded = t.copy_modified(
+            arg_types=arg_types,
+            ret_type=t.ret_type.accept(self),
+            type_guard=(t.type_guard.accept(self) if t.type_guard is not None else None),
+            type_is=(t.type_is.accept(self) if t.type_is is not None else None),
+        )
+        if needs_normalization:
+            return expanded.with_normalized_var_args()
+        return expanded
+
+    def visit_overloaded(self, t: Overloaded) -> Type:
+        items: list[CallableType] = []
+        for item in t.items:
+            new_item = item.accept(self)
+            assert isinstance(new_item, ProperType)
+            assert isinstance(new_item, CallableType)
+            items.append(new_item)
+        return Overloaded(items)
+
+    def expand_type_list_with_unpack(self, typs: list[Type]) -> list[Type]:
+        """Expands a list of types that has an unpack."""
+        items: list[Type] = []
+        for item in typs:
+            if isinstance(item, UnpackType) and isinstance(item.type, TypeVarTupleType):
+                items.extend(self.expand_unpack(item))
+            else:
+                items.append(item.accept(self))
+        return items
+
+    def expand_type_tuple_with_unpack(self, typs: tuple[Type, ...]) -> list[Type]:
+        """Expands a tuple of types that has an unpack."""
+        # Micro-optimization: Specialized variant of expand_type_list_with_unpack
+        items: list[Type] = []
+        for item in typs:
+            if isinstance(item, UnpackType) and isinstance(item.type, TypeVarTupleType):
+                items.extend(self.expand_unpack(item))
+            else:
+                items.append(item.accept(self))
+        return items
+
+    def visit_tuple_type(self, t: TupleType) -> Type:
+        items = self.expand_type_list_with_unpack(t.items)
+        if len(items) == 1:
+            # Normalize Tuple[*Tuple[X, ...]] -> Tuple[X, ...]
+            item = items[0]
+            if isinstance(item, UnpackType):
+                unpacked = get_proper_type(item.type)
+                if isinstance(unpacked, Instance):
+                    # expand_type() may be called during semantic analysis, before invalid unpacks are fixed.
+                    if unpacked.type.fullname != "builtins.tuple":
+                        return t.partial_fallback.accept(self)
+                    if t.partial_fallback.type.fullname != "builtins.tuple":
+                        # If it is a subtype (like named tuple) we need to preserve it,
+                        # this essentially mimics the logic in tuple_fallback().
+                        return t.partial_fallback.accept(self)
+                    return unpacked
+        fallback = t.partial_fallback.accept(self)
+        assert isinstance(fallback, ProperType) and isinstance(fallback, Instance)
+        return t.copy_modified(items=items, fallback=fallback)
+
+    def visit_typeddict_type(self, t: TypedDictType) -> Type:
+        if cached := self.get_cached(t):
+            return cached
+        fallback = t.fallback.accept(self)
+        assert isinstance(fallback, ProperType) and isinstance(fallback, Instance)
+        result = t.copy_modified(item_types=self.expand_types(t.items.values()), fallback=fallback)
+        self.set_cached(t, result)
+        return result
+
+    def visit_literal_type(self, t: LiteralType) -> Type:
+        # TODO: Verify this implementation is correct
+        return t
+
+    def visit_union_type(self, t: UnionType) -> Type:
+        # Use cache to avoid O(n**2) or worse expansion of types during translation
+        # (only for large unions, since caching adds overhead)
+        use_cache = len(t.items) > 3
+        if use_cache and (cached := self.get_cached(t)):
+            return cached
+
+        expanded = self.expand_types(t.items)
+        # After substituting for type variables in t.items, some resulting types
+        # might be subtypes of others, however calling  make_simplified_union()
+        # can cause recursion, so we just remove strict duplicates.
+        simplified = UnionType.make_union(
+            remove_trivial(flatten_nested_unions(expanded)), t.line, t.column
+        )
+        # This call to get_proper_type() is unfortunate but is required to preserve
+        # the invariant that ProperType will stay ProperType after applying expand_type(),
+        # otherwise a single item union of a type alias will break it. Note this should not
+        # cause infinite recursion since pathological aliases like A = Union[A, B] are
+        # banned at the semantic analysis level.
+        result = get_proper_type(simplified)
+
+        if use_cache:
+            self.set_cached(t, result)
+        return result
+
+    def visit_partial_type(self, t: PartialType) -> Type:
+        return t
+
+    def visit_type_type(self, t: TypeType) -> Type:
+        # TODO: Verify that the new item type is valid (instance or
+        # union of instances or Any).  Sadly we can't report errors
+        # here yet.
+        item = t.item.accept(self)
+        return TypeType.make_normalized(item, is_type_form=t.is_type_form)
+
+    def visit_type_alias_type(self, t: TypeAliasType) -> Type:
+        # Target of the type alias cannot contain type variables (not bound by the type
+        # alias itself), so we just expand the arguments.
+        if len(t.args) == 0:
+            return t
+        args = self.expand_type_list_with_unpack(t.args)
+        # TODO: normalize if target is Tuple, and args are [*tuple[X, ...]]?
+        return t.copy_modified(args=args)
+
+    def expand_types(self, types: Iterable[Type]) -> list[Type]:
+        a: list[Type] = []
+        for t in types:
+            a.append(t.accept(self))
+        return a
+
+
+@overload
+def expand_self_type(var: Var, typ: ProperType, replacement: ProperType) -> ProperType: ...
+
+
+@overload
+def expand_self_type(var: Var, typ: Type, replacement: Type) -> Type: ...
+
+
+def expand_self_type(var: Var, typ: Type, replacement: Type) -> Type:
+    """Expand appearances of Self type in a variable type."""
+    if var.info.self_type is not None and not var.is_property:
+        return expand_type(typ, {var.info.self_type.id: replacement})
+    return typ
+
+
+def remove_trivial(types: Iterable[Type]) -> list[Type]:
+    """Make trivial simplifications on a list of types without calling is_subtype().
+
+    This makes following simplifications:
+        * Remove bottom types (taking into account strict optional setting)
+        * Remove everything else if there is an `object`
+        * Remove strict duplicate types
+    """
+    removed_none = False
+    new_types = []
+    all_types = set()
+    for t in types:
+        p_t = get_proper_type(t)
+        if isinstance(p_t, UninhabitedType):
+            continue
+        if isinstance(p_t, NoneType) and not state.strict_optional:
+            removed_none = True
+            continue
+        if isinstance(p_t, Instance) and p_t.type.fullname == "builtins.object":
+            return [p_t]
+        if p_t not in all_types:
+            new_types.append(t)
+            all_types.add(p_t)
+    if new_types:
+        return new_types
+    if removed_none:
+        return [NoneType()]
+    return [UninhabitedType()]

venv/lib/python3.11/site-packages/mypy/exportjson.py

@@ -0,0 +1,612 @@
+"""Tool to convert binary mypy cache files (.ff) to JSON (.ff.json).
+
+Usage:
+   python -m mypy.exportjson .mypy_cache/.../my_module.data.ff
+
+The idea is to make caches introspectable once we've switched to a binary
+cache format and removed support for the older JSON cache format.
+
+This is primarily to support existing use cases that need to inspect
+cache files, and to support debugging mypy caching issues. This means that
+this doesn't necessarily need to be kept 1:1 up to date with changes in the
+binary cache format (to simplify maintenance -- we don't want this to slow
+down mypy development).
+"""
+
+import argparse
+import json
+import sys
+from typing import Any, TypeAlias as _TypeAlias
+
+from librt.internal import ReadBuffer, cache_version
+
+from mypy.cache import CACHE_VERSION, CacheMeta
+from mypy.nodes import (
+    FUNCBASE_FLAGS,
+    FUNCDEF_FLAGS,
+    VAR_FLAGS,
+    ClassDef,
+    DataclassTransformSpec,
+    Decorator,
+    FuncDef,
+    MypyFile,
+    OverloadedFuncDef,
+    OverloadPart,
+    ParamSpecExpr,
+    SymbolNode,
+    SymbolTable,
+    SymbolTableNode,
+    TypeAlias,
+    TypeInfo,
+    TypeVarExpr,
+    TypeVarTupleExpr,
+    Var,
+    get_flags,
+    node_kinds,
+)
+from mypy.types import (
+    NOT_READY,
+    AnyType,
+    CallableType,
+    ExtraAttrs,
+    Instance,
+    LiteralType,
+    NoneType,
+    Overloaded,
+    Parameters,
+    ParamSpecType,
+    TupleType,
+    Type,
+    TypeAliasType,
+    TypedDictType,
+    TypeType,
+    TypeVarTupleType,
+    TypeVarType,
+    UnboundType,
+    UninhabitedType,
+    UnionType,
+    UnpackType,
+    get_proper_type,
+)
+
+Json: _TypeAlias = dict[str, Any] | str
+
+
+class Config:
+    def __init__(self, *, implicit_names: bool = True) -> None:
+        self.implicit_names = implicit_names
+
+
+def convert_binary_cache_to_json(data: bytes, *, implicit_names: bool = True) -> Json:
+    tree = MypyFile.read(ReadBuffer(data))
+    return convert_mypy_file_to_json(tree, Config(implicit_names=implicit_names))
+
+
+def convert_mypy_file_to_json(self: MypyFile, cfg: Config) -> Json:
+    return {
+        ".class": "MypyFile",
+        "_fullname": self._fullname,
+        "names": convert_symbol_table(self.names, cfg),
+        "is_stub": self.is_stub,
+        "path": self.path,
+        "is_partial_stub_package": self.is_partial_stub_package,
+        "future_import_flags": sorted(self.future_import_flags),
+    }
+
+
+def convert_symbol_table(self: SymbolTable, cfg: Config) -> Json:
+    data: dict[str, Any] = {".class": "SymbolTable"}
+    for key, value in self.items():
+        # Skip __builtins__: it's a reference to the builtins
+        # module that gets added to every module by
+        # SemanticAnalyzerPass2.visit_file(), but it shouldn't be
+        # accessed by users of the module.
+        if key == "__builtins__" or value.no_serialize:
+            continue
+        if not cfg.implicit_names and key in {
+            "__spec__",
+            "__package__",
+            "__file__",
+            "__doc__",
+            "__annotations__",
+            "__name__",
+        }:
+            continue
+        data[key] = convert_symbol_table_node(value, cfg)
+    return data
+
+
+def convert_symbol_table_node(self: SymbolTableNode, cfg: Config) -> Json:
+    data: dict[str, Any] = {".class": "SymbolTableNode", "kind": node_kinds[self.kind]}
+    if self.module_hidden:
+        data["module_hidden"] = True
+    if not self.module_public:
+        data["module_public"] = False
+    if self.implicit:
+        data["implicit"] = True
+    if self.plugin_generated:
+        data["plugin_generated"] = True
+    if self.cross_ref:
+        data["cross_ref"] = self.cross_ref
+    elif self.node is not None:
+        data["node"] = convert_symbol_node(self.node, cfg)
+    return data
+
+
+def convert_symbol_node(self: SymbolNode, cfg: Config) -> Json:
+    if isinstance(self, FuncDef):
+        return convert_func_def(self)
+    elif isinstance(self, OverloadedFuncDef):
+        return convert_overloaded_func_def(self)
+    elif isinstance(self, Decorator):
+        return convert_decorator(self)
+    elif isinstance(self, Var):
+        return convert_var(self)
+    elif isinstance(self, TypeInfo):
+        return convert_type_info(self, cfg)
+    elif isinstance(self, TypeAlias):
+        return convert_type_alias(self)
+    elif isinstance(self, TypeVarExpr):
+        return convert_type_var_expr(self)
+    elif isinstance(self, ParamSpecExpr):
+        return convert_param_spec_expr(self)
+    elif isinstance(self, TypeVarTupleExpr):
+        return convert_type_var_tuple_expr(self)
+    return {"ERROR": f"{type(self)!r} unrecognized"}
+
+
+def convert_func_def(self: FuncDef) -> Json:
+    return {
+        ".class": "FuncDef",
+        "name": self._name,
+        "fullname": self._fullname,
+        "arg_names": self.arg_names,
+        "arg_kinds": [int(x.value) for x in self.arg_kinds],
+        "type": None if self.type is None else convert_type(self.type),
+        "flags": get_flags(self, FUNCDEF_FLAGS),
+        "abstract_status": self.abstract_status,
+        # TODO: Do we need expanded, original_def?
+        "dataclass_transform_spec": (
+            None
+            if self.dataclass_transform_spec is None
+            else convert_dataclass_transform_spec(self.dataclass_transform_spec)
+        ),
+        "deprecated": self.deprecated,
+        "original_first_arg": self.original_first_arg,
+    }
+
+
+def convert_dataclass_transform_spec(self: DataclassTransformSpec) -> Json:
+    return {
+        "eq_default": self.eq_default,
+        "order_default": self.order_default,
+        "kw_only_default": self.kw_only_default,
+        "frozen_default": self.frozen_default,
+        "field_specifiers": list(self.field_specifiers),
+    }
+
+
+def convert_overloaded_func_def(self: OverloadedFuncDef) -> Json:
+    return {
+        ".class": "OverloadedFuncDef",
+        "items": [convert_overload_part(i) for i in self.items],
+        "type": None if self.type is None else convert_type(self.type),
+        "fullname": self._fullname,
+        "impl": None if self.impl is None else convert_overload_part(self.impl),
+        "flags": get_flags(self, FUNCBASE_FLAGS),
+        "deprecated": self.deprecated,
+        "setter_index": self.setter_index,
+    }
+
+
+def convert_overload_part(self: OverloadPart) -> Json:
+    if isinstance(self, FuncDef):
+        return convert_func_def(self)
+    else:
+        return convert_decorator(self)
+
+
+def convert_decorator(self: Decorator) -> Json:
+    return {
+        ".class": "Decorator",
+        "func": convert_func_def(self.func),
+        "var": convert_var(self.var),
+        "is_overload": self.is_overload,
+    }
+
+
+def convert_var(self: Var) -> Json:
+    data: dict[str, Any] = {
+        ".class": "Var",
+        "name": self._name,
+        "fullname": self._fullname,
+        "type": None if self.type is None else convert_type(self.type),
+        "setter_type": None if self.setter_type is None else convert_type(self.setter_type),
+        "flags": get_flags(self, VAR_FLAGS),
+    }
+    if self.final_value is not None:
+        data["final_value"] = self.final_value
+    return data
+
+
+def convert_type_info(self: TypeInfo, cfg: Config) -> Json:
+    data = {
+        ".class": "TypeInfo",
+        "module_name": self.module_name,
+        "fullname": self.fullname,
+        "names": convert_symbol_table(self.names, cfg),
+        "defn": convert_class_def(self.defn),
+        "abstract_attributes": self.abstract_attributes,
+        "type_vars": self.type_vars,
+        "has_param_spec_type": self.has_param_spec_type,
+        "bases": [convert_type(b) for b in self.bases],
+        "mro": self._mro_refs,
+        "_promote": [convert_type(p) for p in self._promote],
+        "alt_promote": None if self.alt_promote is None else convert_type(self.alt_promote),
+        "declared_metaclass": (
+            None if self.declared_metaclass is None else convert_type(self.declared_metaclass)
+        ),
+        "metaclass_type": (
+            None if self.metaclass_type is None else convert_type(self.metaclass_type)
+        ),
+        "tuple_type": None if self.tuple_type is None else convert_type(self.tuple_type),
+        "typeddict_type": (
+            None if self.typeddict_type is None else convert_typeddict_type(self.typeddict_type)
+        ),
+        "flags": get_flags(self, TypeInfo.FLAGS),
+        "metadata": self.metadata,
+        "slots": sorted(self.slots) if self.slots is not None else None,
+        "deletable_attributes": self.deletable_attributes,
+        "self_type": convert_type(self.self_type) if self.self_type is not None else None,
+        "dataclass_transform_spec": (
+            convert_dataclass_transform_spec(self.dataclass_transform_spec)
+            if self.dataclass_transform_spec is not None
+            else None
+        ),
+        "deprecated": self.deprecated,
+    }
+    return data
+
+
+def convert_class_def(self: ClassDef) -> Json:
+    return {
+        ".class": "ClassDef",
+        "name": self.name,
+        "fullname": self.fullname,
+        "type_vars": [convert_type(v) for v in self.type_vars],
+    }
+
+
+def convert_type_alias(self: TypeAlias) -> Json:
+    data: Json = {
+        ".class": "TypeAlias",
+        "fullname": self._fullname,
+        "module": self.module,
+        "target": convert_type(self.target),
+        "alias_tvars": [convert_type(v) for v in self.alias_tvars],
+        "no_args": self.no_args,
+        "normalized": self.normalized,
+        "python_3_12_type_alias": self.python_3_12_type_alias,
+    }
+    return data
+
+
+def convert_type_var_expr(self: TypeVarExpr) -> Json:
+    return {
+        ".class": "TypeVarExpr",
+        "name": self._name,
+        "fullname": self._fullname,
+        "values": [convert_type(t) for t in self.values],
+        "upper_bound": convert_type(self.upper_bound),
+        "default": convert_type(self.default),
+        "variance": self.variance,
+    }
+
+
+def convert_param_spec_expr(self: ParamSpecExpr) -> Json:
+    return {
+        ".class": "ParamSpecExpr",
+        "name": self._name,
+        "fullname": self._fullname,
+        "upper_bound": convert_type(self.upper_bound),
+        "default": convert_type(self.default),
+        "variance": self.variance,
+    }
+
+
+def convert_type_var_tuple_expr(self: TypeVarTupleExpr) -> Json:
+    return {
+        ".class": "TypeVarTupleExpr",
+        "name": self._name,
+        "fullname": self._fullname,
+        "upper_bound": convert_type(self.upper_bound),
+        "tuple_fallback": convert_type(self.tuple_fallback),
+        "default": convert_type(self.default),
+        "variance": self.variance,
+    }
+
+
+def convert_type(typ: Type) -> Json:
+    if type(typ) is TypeAliasType:
+        return convert_type_alias_type(typ)
+    typ = get_proper_type(typ)
+    if isinstance(typ, Instance):
+        return convert_instance(typ)
+    elif isinstance(typ, AnyType):
+        return convert_any_type(typ)
+    elif isinstance(typ, NoneType):
+        return convert_none_type(typ)
+    elif isinstance(typ, UnionType):
+        return convert_union_type(typ)
+    elif isinstance(typ, TupleType):
+        return convert_tuple_type(typ)
+    elif isinstance(typ, CallableType):
+        return convert_callable_type(typ)
+    elif isinstance(typ, Overloaded):
+        return convert_overloaded(typ)
+    elif isinstance(typ, LiteralType):
+        return convert_literal_type(typ)
+    elif isinstance(typ, TypeVarType):
+        return convert_type_var_type(typ)
+    elif isinstance(typ, TypeType):
+        return convert_type_type(typ)
+    elif isinstance(typ, UninhabitedType):
+        return convert_uninhabited_type(typ)
+    elif isinstance(typ, UnpackType):
+        return convert_unpack_type(typ)
+    elif isinstance(typ, ParamSpecType):
+        return convert_param_spec_type(typ)
+    elif isinstance(typ, TypeVarTupleType):
+        return convert_type_var_tuple_type(typ)
+    elif isinstance(typ, Parameters):
+        return convert_parameters(typ)
+    elif isinstance(typ, TypedDictType):
+        return convert_typeddict_type(typ)
+    elif isinstance(typ, UnboundType):
+        return convert_unbound_type(typ)
+    return {"ERROR": f"{type(typ)!r} unrecognized"}
+
+
+def convert_instance(self: Instance) -> Json:
+    ready = self.type is not NOT_READY
+    if not self.args and not self.last_known_value and not self.extra_attrs:
+        if ready:
+            return self.type.fullname
+        elif self.type_ref:
+            return self.type_ref
+
+    data: dict[str, Any] = {
+        ".class": "Instance",
+        "type_ref": self.type.fullname if ready else self.type_ref,
+        "args": [convert_type(arg) for arg in self.args],
+    }
+    if self.last_known_value is not None:
+        data["last_known_value"] = convert_type(self.last_known_value)
+    data["extra_attrs"] = convert_extra_attrs(self.extra_attrs) if self.extra_attrs else None
+    return data
+
+
+def convert_extra_attrs(self: ExtraAttrs) -> Json:
+    return {
+        ".class": "ExtraAttrs",
+        "attrs": {k: convert_type(v) for k, v in self.attrs.items()},
+        "immutable": sorted(self.immutable),
+        "mod_name": self.mod_name,
+    }
+
+
+def convert_type_alias_type(self: TypeAliasType) -> Json:
+    data: Json = {
+        ".class": "TypeAliasType",
+        "type_ref": self.type_ref,
+        "args": [convert_type(arg) for arg in self.args],
+    }
+    return data
+
+
+def convert_any_type(self: AnyType) -> Json:
+    return {
+        ".class": "AnyType",
+        "type_of_any": self.type_of_any,
+        "source_any": convert_type(self.source_any) if self.source_any is not None else None,
+        "missing_import_name": self.missing_import_name,
+    }
+
+
+def convert_none_type(self: NoneType) -> Json:
+    return {".class": "NoneType"}
+
+
+def convert_union_type(self: UnionType) -> Json:
+    return {
+        ".class": "UnionType",
+        "items": [convert_type(t) for t in self.items],
+        "uses_pep604_syntax": self.uses_pep604_syntax,
+    }
+
+
+def convert_tuple_type(self: TupleType) -> Json:
+    return {
+        ".class": "TupleType",
+        "items": [convert_type(t) for t in self.items],
+        "partial_fallback": convert_type(self.partial_fallback),
+        "implicit": self.implicit,
+    }
+
+
+def convert_literal_type(self: LiteralType) -> Json:
+    return {".class": "LiteralType", "value": self.value, "fallback": convert_type(self.fallback)}
+
+
+def convert_type_var_type(self: TypeVarType) -> Json:
+    assert not self.id.is_meta_var()
+    return {
+        ".class": "TypeVarType",
+        "name": self.name,
+        "fullname": self.fullname,
+        "id": self.id.raw_id,
+        "namespace": self.id.namespace,
+        "values": [convert_type(v) for v in self.values],
+        "upper_bound": convert_type(self.upper_bound),
+        "default": convert_type(self.default),
+        "variance": self.variance,
+    }
+
+
+def convert_callable_type(self: CallableType) -> Json:
+    return {
+        ".class": "CallableType",
+        "arg_types": [convert_type(t) for t in self.arg_types],
+        "arg_kinds": [int(x.value) for x in self.arg_kinds],
+        "arg_names": self.arg_names,
+        "ret_type": convert_type(self.ret_type),
+        "fallback": convert_type(self.fallback),
+        "name": self.name,
+        # We don't serialize the definition (only used for error messages).
+        "variables": [convert_type(v) for v in self.variables],
+        "is_ellipsis_args": self.is_ellipsis_args,
+        "implicit": self.implicit,
+        "is_bound": self.is_bound,
+        "type_guard": convert_type(self.type_guard) if self.type_guard is not None else None,
+        "type_is": convert_type(self.type_is) if self.type_is is not None else None,
+        "from_concatenate": self.from_concatenate,
+        "imprecise_arg_kinds": self.imprecise_arg_kinds,
+        "unpack_kwargs": self.unpack_kwargs,
+    }
+
+
+def convert_overloaded(self: Overloaded) -> Json:
+    return {".class": "Overloaded", "items": [convert_type(t) for t in self.items]}
+
+
+def convert_type_type(self: TypeType) -> Json:
+    return {".class": "TypeType", "item": convert_type(self.item)}
+
+
+def convert_uninhabited_type(self: UninhabitedType) -> Json:
+    return {".class": "UninhabitedType"}
+
+
+def convert_unpack_type(self: UnpackType) -> Json:
+    return {".class": "UnpackType", "type": convert_type(self.type)}
+
+
+def convert_param_spec_type(self: ParamSpecType) -> Json:
+    assert not self.id.is_meta_var()
+    return {
+        ".class": "ParamSpecType",
+        "name": self.name,
+        "fullname": self.fullname,
+        "id": self.id.raw_id,
+        "namespace": self.id.namespace,
+        "flavor": self.flavor,
+        "upper_bound": convert_type(self.upper_bound),
+        "default": convert_type(self.default),
+        "prefix": convert_type(self.prefix),
+    }
+
+
+def convert_type_var_tuple_type(self: TypeVarTupleType) -> Json:
+    assert not self.id.is_meta_var()
+    return {
+        ".class": "TypeVarTupleType",
+        "name": self.name,
+        "fullname": self.fullname,
+        "id": self.id.raw_id,
+        "namespace": self.id.namespace,
+        "upper_bound": convert_type(self.upper_bound),
+        "tuple_fallback": convert_type(self.tuple_fallback),
+        "default": convert_type(self.default),
+        "min_len": self.min_len,
+    }
+
+
+def convert_parameters(self: Parameters) -> Json:
+    return {
+        ".class": "Parameters",
+        "arg_types": [convert_type(t) for t in self.arg_types],
+        "arg_kinds": [int(x.value) for x in self.arg_kinds],
+        "arg_names": self.arg_names,
+        "variables": [convert_type(tv) for tv in self.variables],
+        "imprecise_arg_kinds": self.imprecise_arg_kinds,
+    }
+
+
+def convert_typeddict_type(self: TypedDictType) -> Json:
+    return {
+        ".class": "TypedDictType",
+        "items": [[n, convert_type(t)] for (n, t) in self.items.items()],
+        "required_keys": sorted(self.required_keys),
+        "readonly_keys": sorted(self.readonly_keys),
+        "fallback": convert_type(self.fallback),
+    }
+
+
+def convert_unbound_type(self: UnboundType) -> Json:
+    return {
+        ".class": "UnboundType",
+        "name": self.name,
+        "args": [convert_type(a) for a in self.args],
+        "expr": self.original_str_expr,
+        "expr_fallback": self.original_str_fallback,
+    }
+
+
+def convert_binary_cache_meta_to_json(data: bytes, data_file: str) -> Json:
+    assert (
+        data[0] == cache_version() and data[1] == CACHE_VERSION
+    ), "Cache file created by an incompatible mypy version"
+    meta = CacheMeta.read(ReadBuffer(data[2:]), data_file)
+    assert meta is not None, f"Error reading meta cache file associated with {data_file}"
+    return {
+        "id": meta.id,
+        "path": meta.path,
+        "mtime": meta.mtime,
+        "size": meta.size,
+        "hash": meta.hash,
+        "data_mtime": meta.data_mtime,
+        "dependencies": meta.dependencies,
+        "suppressed": meta.suppressed,
+        "options": meta.options,
+        "dep_prios": meta.dep_prios,
+        "dep_lines": meta.dep_lines,
+        "dep_hashes": [dep.hex() for dep in meta.dep_hashes],
+        "interface_hash": meta.interface_hash.hex(),
+        "version_id": meta.version_id,
+        "ignore_all": meta.ignore_all,
+        "plugin_data": meta.plugin_data,
+    }
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser(
+        description="Convert binary cache files to JSON. "
+        "Create files in the same directory with extra .json extension."
+    )
+    parser.add_argument(
+        "path", nargs="+", help="mypy cache data file to convert (.data.ff extension)"
+    )
+    args = parser.parse_args()
+    fnams: list[str] = args.path
+    for fnam in fnams:
+        if fnam.endswith(".data.ff"):
+            is_data = True
+        elif fnam.endswith(".meta.ff"):
+            is_data = False
+        else:
+            sys.exit(f"error: Expected .data.ff or .meta.ff extension, but got {fnam}")
+        with open(fnam, "rb") as f:
+            data = f.read()
+        if is_data:
+            json_data = convert_binary_cache_to_json(data)
+        else:
+            data_file = fnam.removesuffix(".meta.ff") + ".data.ff"
+            json_data = convert_binary_cache_meta_to_json(data, data_file)
+        new_fnam = fnam + ".json"
+        with open(new_fnam, "w") as f:
+            json.dump(json_data, f)
+        print(f"{fnam} -> {new_fnam}")
+
+
+if __name__ == "__main__":
+    main()

venv/lib/python3.11/site-packages/mypy/exprtotype.py

@@ -0,0 +1,289 @@
+"""Translate an Expression to a Type value."""
+
+from __future__ import annotations
+
+from collections.abc import Callable
+
+from mypy.fastparse import parse_type_string
+from mypy.nodes import (
+    MISSING_FALLBACK,
+    BytesExpr,
+    CallExpr,
+    ComplexExpr,
+    Context,
+    DictExpr,
+    EllipsisExpr,
+    Expression,
+    FloatExpr,
+    IndexExpr,
+    IntExpr,
+    ListExpr,
+    MemberExpr,
+    NameExpr,
+    OpExpr,
+    RefExpr,
+    StarExpr,
+    StrExpr,
+    SymbolTableNode,
+    TupleExpr,
+    UnaryExpr,
+    get_member_expr_fullname,
+)
+from mypy.options import Options
+from mypy.types import (
+    ANNOTATED_TYPE_NAMES,
+    AnyType,
+    CallableArgument,
+    EllipsisType,
+    Instance,
+    ProperType,
+    RawExpressionType,
+    Type,
+    TypedDictType,
+    TypeList,
+    TypeOfAny,
+    UnboundType,
+    UnionType,
+    UnpackType,
+)
+
+
+class TypeTranslationError(Exception):
+    """Exception raised when an expression is not valid as a type."""
+
+
+def _extract_argument_name(expr: Expression) -> str | None:
+    if isinstance(expr, NameExpr) and expr.name == "None":
+        return None
+    elif isinstance(expr, StrExpr):
+        return expr.value
+    else:
+        raise TypeTranslationError()
+
+
+def expr_to_unanalyzed_type(
+    expr: Expression,
+    options: Options,
+    allow_new_syntax: bool = False,
+    _parent: Expression | None = None,
+    allow_unpack: bool = False,
+    lookup_qualified: Callable[[str, Context], SymbolTableNode | None] | None = None,
+) -> ProperType:
+    """Translate an expression to the corresponding type.
+
+    The result is not semantically analyzed. It can be UnboundType or TypeList.
+    Raise TypeTranslationError if the expression cannot represent a type.
+
+    If lookup_qualified is not provided, the expression is expected to be semantically
+    analyzed.
+
+    If allow_new_syntax is True, allow all type syntax independent of the target
+    Python version (used in stubs).
+
+    # TODO: a lot of code here is duplicated in fastparse.py, refactor this.
+    """
+    # The `parent` parameter is used in recursive calls to provide context for
+    # understanding whether an CallableArgument is ok.
+    name: str | None = None
+    if isinstance(expr, NameExpr):
+        name = expr.name
+        if name == "True":
+            return RawExpressionType(True, "builtins.bool", line=expr.line, column=expr.column)
+        elif name == "False":
+            return RawExpressionType(False, "builtins.bool", line=expr.line, column=expr.column)
+        else:
+            return UnboundType(name, line=expr.line, column=expr.column)
+    elif isinstance(expr, MemberExpr):
+        fullname = get_member_expr_fullname(expr)
+        if fullname:
+            return UnboundType(fullname, line=expr.line, column=expr.column)
+        else:
+            raise TypeTranslationError()
+    elif isinstance(expr, IndexExpr):
+        base = expr_to_unanalyzed_type(
+            expr.base, options, allow_new_syntax, expr, lookup_qualified=lookup_qualified
+        )
+        if isinstance(base, UnboundType):
+            if base.args:
+                raise TypeTranslationError()
+            if isinstance(expr.index, TupleExpr):
+                args = expr.index.items
+            else:
+                args = [expr.index]
+
+            if isinstance(expr.base, RefExpr):
+                # Check if the type is Annotated[...]. For this we need the fullname,
+                # which must be looked up if the expression hasn't been semantically analyzed.
+                base_fullname = None
+                if lookup_qualified is not None:
+                    sym = lookup_qualified(base.name, expr)
+                    if sym and sym.node:
+                        base_fullname = sym.node.fullname
+                else:
+                    base_fullname = expr.base.fullname
+
+                if base_fullname is not None and base_fullname in ANNOTATED_TYPE_NAMES:
+                    # TODO: this is not the optimal solution as we are basically getting rid
+                    # of the Annotation definition and only returning the type information,
+                    # losing all the annotations.
+                    return expr_to_unanalyzed_type(
+                        args[0], options, allow_new_syntax, expr, lookup_qualified=lookup_qualified
+                    )
+            base.args = tuple(
+                expr_to_unanalyzed_type(
+                    arg,
+                    options,
+                    allow_new_syntax,
+                    expr,
+                    allow_unpack=True,
+                    lookup_qualified=lookup_qualified,
+                )
+                for arg in args
+            )
+            if not base.args:
+                base.empty_tuple_index = True
+            return base
+        else:
+            raise TypeTranslationError()
+    elif (
+        isinstance(expr, OpExpr)
+        and expr.op == "|"
+        and ((options.python_version >= (3, 10)) or allow_new_syntax)
+    ):
+        return UnionType(
+            [
+                expr_to_unanalyzed_type(
+                    expr.left, options, allow_new_syntax, lookup_qualified=lookup_qualified
+                ),
+                expr_to_unanalyzed_type(
+                    expr.right, options, allow_new_syntax, lookup_qualified=lookup_qualified
+                ),
+            ],
+            uses_pep604_syntax=True,
+        )
+    elif isinstance(expr, CallExpr) and isinstance(_parent, ListExpr):
+        c = expr.callee
+        names = []
+        # Go through the dotted member expr chain to get the full arg
+        # constructor name to look up
+        while True:
+            if isinstance(c, NameExpr):
+                names.append(c.name)
+                break
+            elif isinstance(c, MemberExpr):
+                names.append(c.name)
+                c = c.expr
+            else:
+                raise TypeTranslationError()
+        arg_const = ".".join(reversed(names))
+
+        # Go through the constructor args to get its name and type.
+        name = None
+        default_type = AnyType(TypeOfAny.unannotated)
+        typ: Type = default_type
+        for i, arg in enumerate(expr.args):
+            if expr.arg_names[i] is not None:
+                if expr.arg_names[i] == "name":
+                    if name is not None:
+                        # Two names
+                        raise TypeTranslationError()
+                    name = _extract_argument_name(arg)
+                    continue
+                elif expr.arg_names[i] == "type":
+                    if typ is not default_type:
+                        # Two types
+                        raise TypeTranslationError()
+                    typ = expr_to_unanalyzed_type(
+                        arg, options, allow_new_syntax, expr, lookup_qualified=lookup_qualified
+                    )
+                    continue
+                else:
+                    raise TypeTranslationError()
+            elif i == 0:
+                typ = expr_to_unanalyzed_type(
+                    arg, options, allow_new_syntax, expr, lookup_qualified=lookup_qualified
+                )
+            elif i == 1:
+                name = _extract_argument_name(arg)
+            else:
+                raise TypeTranslationError()
+        return CallableArgument(typ, name, arg_const, expr.line, expr.column)
+    elif isinstance(expr, ListExpr):
+        return TypeList(
+            [
+                expr_to_unanalyzed_type(
+                    t,
+                    options,
+                    allow_new_syntax,
+                    expr,
+                    allow_unpack=True,
+                    lookup_qualified=lookup_qualified,
+                )
+                for t in expr.items
+            ],
+            line=expr.line,
+            column=expr.column,
+        )
+    elif isinstance(expr, StrExpr):
+        return parse_type_string(expr.value, "builtins.str", expr.line, expr.column)
+    elif isinstance(expr, BytesExpr):
+        return parse_type_string(expr.value, "builtins.bytes", expr.line, expr.column)
+    elif isinstance(expr, UnaryExpr):
+        typ = expr_to_unanalyzed_type(
+            expr.expr, options, allow_new_syntax, lookup_qualified=lookup_qualified
+        )
+        if isinstance(typ, RawExpressionType):
+            if isinstance(typ.literal_value, int):
+                if expr.op == "-":
+                    typ.literal_value *= -1
+                    return typ
+                elif expr.op == "+":
+                    return typ
+        raise TypeTranslationError()
+    elif isinstance(expr, IntExpr):
+        return RawExpressionType(expr.value, "builtins.int", line=expr.line, column=expr.column)
+    elif isinstance(expr, FloatExpr):
+        # Floats are not valid parameters for RawExpressionType , so we just
+        # pass in 'None' for now. We'll report the appropriate error at a later stage.
+        return RawExpressionType(None, "builtins.float", line=expr.line, column=expr.column)
+    elif isinstance(expr, ComplexExpr):
+        # Same thing as above with complex numbers.
+        return RawExpressionType(None, "builtins.complex", line=expr.line, column=expr.column)
+    elif isinstance(expr, EllipsisExpr):
+        return EllipsisType(expr.line)
+    elif allow_unpack and isinstance(expr, StarExpr):
+        return UnpackType(
+            expr_to_unanalyzed_type(
+                expr.expr, options, allow_new_syntax, lookup_qualified=lookup_qualified
+            ),
+            from_star_syntax=True,
+        )
+    elif isinstance(expr, DictExpr):
+        if not expr.items:
+            raise TypeTranslationError()
+        items: dict[str, Type] = {}
+        extra_items_from = []
+        for item_name, value in expr.items:
+            if not isinstance(item_name, StrExpr):
+                if item_name is None:
+                    extra_items_from.append(
+                        expr_to_unanalyzed_type(
+                            value,
+                            options,
+                            allow_new_syntax,
+                            expr,
+                            lookup_qualified=lookup_qualified,
+                        )
+                    )
+                    continue
+                raise TypeTranslationError()
+            items[item_name.value] = expr_to_unanalyzed_type(
+                value, options, allow_new_syntax, expr, lookup_qualified=lookup_qualified
+            )
+        result = TypedDictType(
+            items, set(), set(), Instance(MISSING_FALLBACK, ()), expr.line, expr.column
+        )
+        result.extra_items_from = extra_items_from
+        return result
+    else:
+        raise TypeTranslationError()

venv/lib/python3.11/site-packages/mypy/find_sources.py

@@ -0,0 +1,257 @@
+"""Routines for finding the sources that mypy will check"""
+
+from __future__ import annotations
+
+import functools
+import os
+from collections.abc import Sequence
+from typing import Final
+
+from mypy.fscache import FileSystemCache
+from mypy.modulefinder import (
+    PYTHON_EXTENSIONS,
+    BuildSource,
+    matches_exclude,
+    matches_gitignore,
+    mypy_path,
+)
+from mypy.options import Options
+
+PY_EXTENSIONS: Final = tuple(PYTHON_EXTENSIONS)
+
+
+class InvalidSourceList(Exception):
+    """Exception indicating a problem in the list of sources given to mypy."""
+
+
+def create_source_list(
+    paths: Sequence[str],
+    options: Options,
+    fscache: FileSystemCache | None = None,
+    allow_empty_dir: bool = False,
+) -> list[BuildSource]:
+    """From a list of source files/directories, makes a list of BuildSources.
+
+    Raises InvalidSourceList on errors.
+    """
+    fscache = fscache or FileSystemCache()
+    finder = SourceFinder(fscache, options)
+
+    sources = []
+    for path in paths:
+        path = os.path.normpath(path)
+        if path.endswith(PY_EXTENSIONS):
+            # Can raise InvalidSourceList if a directory doesn't have a valid module name.
+            name, base_dir = finder.crawl_up(path)
+            sources.append(BuildSource(path, name, None, base_dir))
+        elif fscache.isdir(path):
+            sub_sources = finder.find_sources_in_dir(path)
+            if not sub_sources and not allow_empty_dir:
+                raise InvalidSourceList(f"There are no .py[i] files in directory '{path}'")
+            sources.extend(sub_sources)
+        else:
+            mod = os.path.basename(path) if options.scripts_are_modules else None
+            sources.append(BuildSource(path, mod, None))
+    return sources
+
+
+def keyfunc(name: str) -> tuple[bool, int, str]:
+    """Determines sort order for directory listing.
+
+    The desirable properties are:
+    1) foo < foo.pyi < foo.py
+    2) __init__.py[i] < foo
+    """
+    base, suffix = os.path.splitext(name)
+    for i, ext in enumerate(PY_EXTENSIONS):
+        if suffix == ext:
+            return (base != "__init__", i, base)
+    return (base != "__init__", -1, name)
+
+
+def normalise_package_base(root: str) -> str:
+    if not root:
+        root = os.curdir
+    root = os.path.abspath(root)
+    if root.endswith(os.sep):
+        root = root[:-1]
+    return root
+
+
+def get_explicit_package_bases(options: Options) -> list[str] | None:
+    """Returns explicit package bases to use if the option is enabled, or None if disabled.
+
+    We currently use MYPYPATH and the current directory as the package bases. In the future,
+    when --namespace-packages is the default could also use the values passed with the
+    --package-root flag, see #9632.
+
+    Values returned are normalised so we can use simple string comparisons in
+    SourceFinder.is_explicit_package_base
+    """
+    if not options.explicit_package_bases:
+        return None
+    roots = mypy_path() + options.mypy_path + [os.getcwd()]
+    return [normalise_package_base(root) for root in roots]
+
+
+class SourceFinder:
+    def __init__(self, fscache: FileSystemCache, options: Options) -> None:
+        self.fscache = fscache
+        self.explicit_package_bases = get_explicit_package_bases(options)
+        self.namespace_packages = options.namespace_packages
+        self.exclude = options.exclude
+        self.exclude_gitignore = options.exclude_gitignore
+        self.verbosity = options.verbosity
+
+    def is_explicit_package_base(self, path: str) -> bool:
+        assert self.explicit_package_bases
+        return normalise_package_base(path) in self.explicit_package_bases
+
+    def find_sources_in_dir(self, path: str) -> list[BuildSource]:
+        sources = []
+
+        seen: set[str] = set()
+        names = sorted(self.fscache.listdir(path), key=keyfunc)
+        for name in names:
+            # Skip certain names altogether
+            if name in ("__pycache__", "site-packages", "node_modules") or name.startswith("."):
+                continue
+            subpath = os.path.join(path, name)
+
+            if matches_exclude(subpath, self.exclude, self.fscache, self.verbosity >= 2):
+                continue
+            if self.exclude_gitignore and matches_gitignore(
+                subpath, self.fscache, self.verbosity >= 2
+            ):
+                continue
+
+            if self.fscache.isdir(subpath):
+                sub_sources = self.find_sources_in_dir(subpath)
+                if sub_sources:
+                    seen.add(name)
+                    sources.extend(sub_sources)
+            else:
+                stem, suffix = os.path.splitext(name)
+                if stem not in seen and suffix in PY_EXTENSIONS:
+                    seen.add(stem)
+                    module, base_dir = self.crawl_up(subpath)
+                    sources.append(BuildSource(subpath, module, None, base_dir))
+
+        return sources
+
+    def crawl_up(self, path: str) -> tuple[str, str]:
+        """Given a .py[i] filename, return module and base directory.
+
+        For example, given "xxx/yyy/foo/bar.py", we might return something like:
+        ("foo.bar", "xxx/yyy")
+
+        If namespace packages is off, we crawl upwards until we find a directory without
+        an __init__.py
+
+        If namespace packages is on, we crawl upwards until the nearest explicit base directory.
+        Failing that, we return one past the highest directory containing an __init__.py
+
+        We won't crawl past directories with invalid package names.
+        The base directory returned is an absolute path.
+        """
+        path = os.path.abspath(path)
+        parent, filename = os.path.split(path)
+
+        module_name = strip_py(filename) or filename
+
+        parent_module, base_dir = self.crawl_up_dir(parent)
+        if module_name == "__init__":
+            return parent_module, base_dir
+
+        # Note that module_name might not actually be a valid identifier, but that's okay
+        # Ignoring this possibility sidesteps some search path confusion
+        module = module_join(parent_module, module_name)
+        return module, base_dir
+
+    def crawl_up_dir(self, dir: str) -> tuple[str, str]:
+        return self._crawl_up_helper(dir) or ("", dir)
+
+    @functools.lru_cache  # noqa: B019
+    def _crawl_up_helper(self, dir: str) -> tuple[str, str] | None:
+        """Given a directory, maybe returns module and base directory.
+
+        We return a non-None value if we were able to find something clearly intended as a base
+        directory (as adjudicated by being an explicit base directory or by containing a package
+        with __init__.py).
+
+        This distinction is necessary for namespace packages, so that we know when to treat
+        ourselves as a subpackage.
+        """
+        # stop crawling if we're an explicit base directory
+        if self.explicit_package_bases is not None and self.is_explicit_package_base(dir):
+            return "", dir
+
+        parent, name = os.path.split(dir)
+        name = name.removesuffix("-stubs")  # PEP-561 stub-only directory
+
+        # recurse if there's an __init__.py
+        init_file = self.get_init_file(dir)
+        if init_file is not None:
+            if not name.isidentifier():
+                # in most cases the directory name is invalid, we'll just stop crawling upwards
+                # but if there's an __init__.py in the directory, something is messed up
+                raise InvalidSourceList(
+                    f"{name} contains {os.path.basename(init_file)} "
+                    "but is not a valid Python package name"
+                )
+            # we're definitely a package, so we always return a non-None value
+            mod_prefix, base_dir = self.crawl_up_dir(parent)
+            return module_join(mod_prefix, name), base_dir
+
+        # stop crawling if we're out of path components or our name is an invalid identifier
+        if not name or not parent or not name.isidentifier():
+            return None
+
+        # stop crawling if namespace packages is off (since we don't have an __init__.py)
+        if not self.namespace_packages:
+            return None
+
+        # at this point: namespace packages is on, we don't have an __init__.py and we're not an
+        # explicit base directory
+        result = self._crawl_up_helper(parent)
+        if result is None:
+            # we're not an explicit base directory and we don't have an __init__.py
+            # and none of our parents are either, so return
+            return None
+        # one of our parents was an explicit base directory or had an __init__.py, so we're
+        # definitely a subpackage! chain our name to the module.
+        mod_prefix, base_dir = result
+        return module_join(mod_prefix, name), base_dir
+
+    def get_init_file(self, dir: str) -> str | None:
+        """Check whether a directory contains a file named __init__.py[i].
+
+        If so, return the file's name (with dir prefixed).  If not, return None.
+
+        This prefers .pyi over .py (because of the ordering of PY_EXTENSIONS).
+        """
+        for ext in PY_EXTENSIONS:
+            f = os.path.join(dir, "__init__" + ext)
+            if self.fscache.isfile(f):
+                return f
+            if ext == ".py" and self.fscache.init_under_package_root(f):
+                return f
+        return None
+
+
+def module_join(parent: str, child: str) -> str:
+    """Join module ids, accounting for a possibly empty parent."""
+    if parent:
+        return parent + "." + child
+    return child
+
+
+def strip_py(arg: str) -> str | None:
+    """Strip a trailing .py or .pyi suffix.
+
+    Return None if no such suffix is found.
+    """
+    for ext in PY_EXTENSIONS:
+        if arg.endswith(ext):
+            return arg[: -len(ext)]
+    return None

venv/lib/python3.11/site-packages/mypy/fixup.py

@@ -0,0 +1,444 @@
+"""Fix up various things after deserialization."""
+
+from __future__ import annotations
+
+from typing import Any, Final
+
+from mypy.lookup import lookup_fully_qualified
+from mypy.nodes import (
+    Block,
+    ClassDef,
+    Decorator,
+    FuncDef,
+    MypyFile,
+    OverloadedFuncDef,
+    ParamSpecExpr,
+    SymbolTable,
+    TypeAlias,
+    TypeInfo,
+    TypeVarExpr,
+    TypeVarTupleExpr,
+    Var,
+)
+from mypy.types import (
+    NOT_READY,
+    AnyType,
+    CallableType,
+    Instance,
+    LiteralType,
+    Overloaded,
+    Parameters,
+    ParamSpecType,
+    ProperType,
+    TupleType,
+    TypeAliasType,
+    TypedDictType,
+    TypeOfAny,
+    TypeType,
+    TypeVarTupleType,
+    TypeVarType,
+    TypeVisitor,
+    UnboundType,
+    UnionType,
+    UnpackType,
+)
+from mypy.visitor import NodeVisitor
+
+
+# N.B: we do a allow_missing fixup when fixing up a fine-grained
+# incremental cache load (since there may be cross-refs into deleted
+# modules)
+def fixup_module(tree: MypyFile, modules: dict[str, MypyFile], allow_missing: bool) -> None:
+    node_fixer = NodeFixer(modules, allow_missing)
+    node_fixer.visit_symbol_table(tree.names, tree.fullname)
+
+
+# TODO: Fix up .info when deserializing, i.e. much earlier.
+class NodeFixer(NodeVisitor[None]):
+    current_info: TypeInfo | None = None
+
+    def __init__(self, modules: dict[str, MypyFile], allow_missing: bool) -> None:
+        self.modules = modules
+        self.allow_missing = allow_missing
+        self.type_fixer = TypeFixer(self.modules, allow_missing)
+
+    # NOTE: This method isn't (yet) part of the NodeVisitor API.
+    def visit_type_info(self, info: TypeInfo) -> None:
+        save_info = self.current_info
+        try:
+            self.current_info = info
+            if info.defn:
+                info.defn.accept(self)
+            if info.names:
+                self.visit_symbol_table(info.names, info.fullname)
+            if info.bases:
+                for base in info.bases:
+                    base.accept(self.type_fixer)
+            if info._promote:
+                for p in info._promote:
+                    p.accept(self.type_fixer)
+            if info.tuple_type:
+                info.tuple_type.accept(self.type_fixer)
+                info.update_tuple_type(info.tuple_type)
+                if info.special_alias:
+                    info.special_alias.alias_tvars = list(info.defn.type_vars)
+                    for i, t in enumerate(info.defn.type_vars):
+                        if isinstance(t, TypeVarTupleType):
+                            info.special_alias.tvar_tuple_index = i
+            if info.typeddict_type:
+                info.typeddict_type.accept(self.type_fixer)
+                info.update_typeddict_type(info.typeddict_type)
+                if info.special_alias:
+                    info.special_alias.alias_tvars = list(info.defn.type_vars)
+                    for i, t in enumerate(info.defn.type_vars):
+                        if isinstance(t, TypeVarTupleType):
+                            info.special_alias.tvar_tuple_index = i
+            if info.declared_metaclass:
+                info.declared_metaclass.accept(self.type_fixer)
+            if info.metaclass_type:
+                info.metaclass_type.accept(self.type_fixer)
+            if info.self_type:
+                info.self_type.accept(self.type_fixer)
+            if info.alt_promote:
+                info.alt_promote.accept(self.type_fixer)
+                instance = Instance(info, [])
+                # Hack: We may also need to add a backwards promotion (from int to native int),
+                # since it might not be serialized.
+                if instance not in info.alt_promote.type._promote:
+                    info.alt_promote.type._promote.append(instance)
+            if info._mro_refs:
+                info.mro = [
+                    lookup_fully_qualified_typeinfo(
+                        self.modules, name, allow_missing=self.allow_missing
+                    )
+                    for name in info._mro_refs
+                ]
+                info._mro_refs = None
+        finally:
+            self.current_info = save_info
+
+    # NOTE: This method *definitely* isn't part of the NodeVisitor API.
+    def visit_symbol_table(self, symtab: SymbolTable, table_fullname: str) -> None:
+        # Copy the items because we may mutate symtab.
+        for key in list(symtab):
+            value = symtab[key]
+            cross_ref = value.cross_ref
+            if cross_ref is not None:  # Fix up cross-reference.
+                value.cross_ref = None
+                if cross_ref in self.modules:
+                    value.node = self.modules[cross_ref]
+                else:
+                    stnode = lookup_fully_qualified(
+                        cross_ref, self.modules, raise_on_missing=not self.allow_missing
+                    )
+                    if stnode is not None:
+                        if stnode is value:
+                            # The node seems to refer to itself, which can mean that
+                            # the target is a deleted submodule of the current module,
+                            # and thus lookup falls back to the symbol table of the parent
+                            # package. Here's how this may happen:
+                            #
+                            #   pkg/__init__.py:
+                            #     from pkg import sub
+                            #
+                            # Now if pkg.sub is deleted, the pkg.sub symbol table entry
+                            # appears to refer to itself. Replace the entry with a
+                            # placeholder to avoid a crash. We can't delete the entry,
+                            # as it would stop dependency propagation.
+                            value.node = Var(key + "@deleted")
+                        else:
+                            assert stnode.node is not None, (table_fullname + "." + key, cross_ref)
+                            value.node = stnode.node
+                    elif not self.allow_missing:
+                        assert False, f"Could not find cross-ref {cross_ref}"
+                    else:
+                        # We have a missing crossref in allow missing mode, need to put something
+                        value.node = missing_info(self.modules)
+            else:
+                if isinstance(value.node, TypeInfo):
+                    # TypeInfo has no accept().  TODO: Add it?
+                    self.visit_type_info(value.node)
+                elif value.node is not None:
+                    value.node.accept(self)
+                else:
+                    assert False, f"Unexpected empty node {key!r}: {value}"
+
+    def visit_func_def(self, func: FuncDef) -> None:
+        if self.current_info is not None:
+            func.info = self.current_info
+        if func.type is not None:
+            func.type.accept(self.type_fixer)
+            if isinstance(func.type, CallableType):
+                func.type.definition = func
+
+    def visit_overloaded_func_def(self, o: OverloadedFuncDef) -> None:
+        if self.current_info is not None:
+            o.info = self.current_info
+        if o.type:
+            o.type.accept(self.type_fixer)
+        for item in o.items:
+            item.accept(self)
+        if o.impl:
+            o.impl.accept(self)
+        if isinstance(o.type, Overloaded):
+            # For error messages we link the original definition for each item.
+            for typ, item in zip(o.type.items, o.items):
+                typ.definition = item
+
+    def visit_decorator(self, d: Decorator) -> None:
+        if self.current_info is not None:
+            d.var.info = self.current_info
+        if d.func:
+            d.func.accept(self)
+        if d.var:
+            d.var.accept(self)
+        for node in d.decorators:
+            node.accept(self)
+        typ = d.var.type
+        if isinstance(typ, ProperType) and isinstance(typ, CallableType):
+            typ.definition = d.func
+
+    def visit_class_def(self, c: ClassDef) -> None:
+        for v in c.type_vars:
+            v.accept(self.type_fixer)
+
+    def visit_type_var_expr(self, tv: TypeVarExpr) -> None:
+        for value in tv.values:
+            value.accept(self.type_fixer)
+        tv.upper_bound.accept(self.type_fixer)
+        tv.default.accept(self.type_fixer)
+
+    def visit_paramspec_expr(self, p: ParamSpecExpr) -> None:
+        p.upper_bound.accept(self.type_fixer)
+        p.default.accept(self.type_fixer)
+
+    def visit_type_var_tuple_expr(self, tv: TypeVarTupleExpr) -> None:
+        tv.upper_bound.accept(self.type_fixer)
+        tv.tuple_fallback.accept(self.type_fixer)
+        tv.default.accept(self.type_fixer)
+
+    def visit_var(self, v: Var) -> None:
+        if self.current_info is not None:
+            v.info = self.current_info
+        if v.type is not None:
+            v.type.accept(self.type_fixer)
+        if v.setter_type is not None:
+            v.setter_type.accept(self.type_fixer)
+
+    def visit_type_alias(self, a: TypeAlias) -> None:
+        a.target.accept(self.type_fixer)
+        for v in a.alias_tvars:
+            v.accept(self.type_fixer)
+
+
+class TypeFixer(TypeVisitor[None]):
+    def __init__(self, modules: dict[str, MypyFile], allow_missing: bool) -> None:
+        self.modules = modules
+        self.allow_missing = allow_missing
+
+    def visit_instance(self, inst: Instance) -> None:
+        # TODO: Combine Instances that are exactly the same?
+        type_ref = inst.type_ref
+        if type_ref is None:
+            return  # We've already been here.
+        inst.type_ref = None
+        inst.type = lookup_fully_qualified_typeinfo(
+            self.modules, type_ref, allow_missing=self.allow_missing
+        )
+        # TODO: Is this needed or redundant?
+        # Also fix up the bases, just in case.
+        for base in inst.type.bases:
+            if base.type is NOT_READY:
+                base.accept(self)
+        for a in inst.args:
+            a.accept(self)
+        if inst.last_known_value is not None:
+            inst.last_known_value.accept(self)
+        if inst.extra_attrs:
+            for v in inst.extra_attrs.attrs.values():
+                v.accept(self)
+
+    def visit_type_alias_type(self, t: TypeAliasType) -> None:
+        type_ref = t.type_ref
+        if type_ref is None:
+            return  # We've already been here.
+        t.type_ref = None
+        t.alias = lookup_fully_qualified_alias(
+            self.modules, type_ref, allow_missing=self.allow_missing
+        )
+        for a in t.args:
+            a.accept(self)
+
+    def visit_any(self, o: Any) -> None:
+        pass  # Nothing to descend into.
+
+    def visit_callable_type(self, ct: CallableType) -> None:
+        if ct.fallback:
+            ct.fallback.accept(self)
+        for argt in ct.arg_types:
+            # argt may be None, e.g. for __self in NamedTuple constructors.
+            if argt is not None:
+                argt.accept(self)
+        if ct.ret_type is not None:
+            ct.ret_type.accept(self)
+        for v in ct.variables:
+            v.accept(self)
+        if ct.type_guard is not None:
+            ct.type_guard.accept(self)
+        if ct.type_is is not None:
+            ct.type_is.accept(self)
+
+    def visit_overloaded(self, t: Overloaded) -> None:
+        for ct in t.items:
+            ct.accept(self)
+
+    def visit_erased_type(self, o: Any) -> None:
+        # This type should exist only temporarily during type inference
+        raise RuntimeError("Shouldn't get here", o)
+
+    def visit_deleted_type(self, o: Any) -> None:
+        pass  # Nothing to descend into.
+
+    def visit_none_type(self, o: Any) -> None:
+        pass  # Nothing to descend into.
+
+    def visit_uninhabited_type(self, o: Any) -> None:
+        pass  # Nothing to descend into.
+
+    def visit_partial_type(self, o: Any) -> None:
+        raise RuntimeError("Shouldn't get here", o)
+
+    def visit_tuple_type(self, tt: TupleType) -> None:
+        if tt.items:
+            for it in tt.items:
+                it.accept(self)
+        if tt.partial_fallback is not None:
+            tt.partial_fallback.accept(self)
+
+    def visit_typeddict_type(self, tdt: TypedDictType) -> None:
+        if tdt.items:
+            for it in tdt.items.values():
+                it.accept(self)
+        if tdt.fallback is not None:
+            if tdt.fallback.type_ref is not None:
+                if (
+                    lookup_fully_qualified(
+                        tdt.fallback.type_ref,
+                        self.modules,
+                        raise_on_missing=not self.allow_missing,
+                    )
+                    is None
+                ):
+                    # We reject fake TypeInfos for TypedDict fallbacks because
+                    # the latter are used in type checking and must be valid.
+                    tdt.fallback.type_ref = "typing._TypedDict"
+            tdt.fallback.accept(self)
+
+    def visit_literal_type(self, lt: LiteralType) -> None:
+        lt.fallback.accept(self)
+
+    def visit_type_var(self, tvt: TypeVarType) -> None:
+        if tvt.values:
+            for vt in tvt.values:
+                vt.accept(self)
+        tvt.upper_bound.accept(self)
+        tvt.default.accept(self)
+
+    def visit_param_spec(self, p: ParamSpecType) -> None:
+        p.upper_bound.accept(self)
+        p.default.accept(self)
+        p.prefix.accept(self)
+
+    def visit_type_var_tuple(self, t: TypeVarTupleType) -> None:
+        t.tuple_fallback.accept(self)
+        t.upper_bound.accept(self)
+        t.default.accept(self)
+
+    def visit_unpack_type(self, u: UnpackType) -> None:
+        u.type.accept(self)
+
+    def visit_parameters(self, p: Parameters) -> None:
+        for argt in p.arg_types:
+            if argt is not None:
+                argt.accept(self)
+        for var in p.variables:
+            var.accept(self)
+
+    def visit_unbound_type(self, o: UnboundType) -> None:
+        for a in o.args:
+            a.accept(self)
+
+    def visit_union_type(self, ut: UnionType) -> None:
+        if ut.items:
+            for it in ut.items:
+                it.accept(self)
+
+    def visit_type_type(self, t: TypeType) -> None:
+        t.item.accept(self)
+
+
+def lookup_fully_qualified_typeinfo(
+    modules: dict[str, MypyFile], name: str, *, allow_missing: bool
+) -> TypeInfo:
+    stnode = lookup_fully_qualified(name, modules, raise_on_missing=not allow_missing)
+    node = stnode.node if stnode else None
+    if isinstance(node, TypeInfo):
+        return node
+    else:
+        # Looks like a missing TypeInfo during an initial daemon load, put something there
+        assert (
+            allow_missing
+        ), "Should never get here in normal mode, got {}:{} instead of TypeInfo".format(
+            type(node).__name__, node.fullname if node else ""
+        )
+        return missing_info(modules)
+
+
+def lookup_fully_qualified_alias(
+    modules: dict[str, MypyFile], name: str, *, allow_missing: bool
+) -> TypeAlias:
+    stnode = lookup_fully_qualified(name, modules, raise_on_missing=not allow_missing)
+    node = stnode.node if stnode else None
+    if isinstance(node, TypeAlias):
+        return node
+    elif isinstance(node, TypeInfo):
+        if node.special_alias:
+            # Already fixed up.
+            return node.special_alias
+        if node.tuple_type:
+            alias = TypeAlias.from_tuple_type(node)
+        elif node.typeddict_type:
+            alias = TypeAlias.from_typeddict_type(node)
+        else:
+            assert allow_missing
+            return missing_alias()
+        node.special_alias = alias
+        return alias
+    else:
+        # Looks like a missing TypeAlias during an initial daemon load, put something there
+        assert (
+            allow_missing
+        ), "Should never get here in normal mode, got {}:{} instead of TypeAlias".format(
+            type(node).__name__, node.fullname if node else ""
+        )
+        return missing_alias()
+
+
+_SUGGESTION: Final = "<missing {}: *should* have gone away during fine-grained update>"
+
+
+def missing_info(modules: dict[str, MypyFile]) -> TypeInfo:
+    suggestion = _SUGGESTION.format("info")
+    dummy_def = ClassDef(suggestion, Block([]))
+    dummy_def.fullname = suggestion
+
+    info = TypeInfo(SymbolTable(), dummy_def, "<missing>")
+    obj_type = lookup_fully_qualified_typeinfo(modules, "builtins.object", allow_missing=False)
+    info.bases = [Instance(obj_type, [])]
+    info.mro = [info, obj_type]
+    return info
+
+
+def missing_alias() -> TypeAlias:
+    suggestion = _SUGGESTION.format("alias")
+    return TypeAlias(AnyType(TypeOfAny.special_form), suggestion, "<missing>", line=-1, column=-1)

venv/lib/python3.11/site-packages/mypy/freetree.py

@@ -0,0 +1,23 @@
+"""Generic node traverser visitor"""
+
+from __future__ import annotations
+
+from mypy.nodes import Block, MypyFile
+from mypy.traverser import TraverserVisitor
+
+
+class TreeFreer(TraverserVisitor):
+    def visit_block(self, block: Block) -> None:
+        super().visit_block(block)
+        block.body.clear()
+
+
+def free_tree(tree: MypyFile) -> None:
+    """Free all the ASTs associated with a module.
+
+    This needs to be done recursively, since symbol tables contain
+    references to definitions, so those won't be freed but we want their
+    contents to be.
+    """
+    tree.accept(TreeFreer())
+    tree.defs.clear()

venv/lib/python3.11/site-packages/mypy/fscache.py

@@ -0,0 +1,307 @@
+"""Interface for accessing the file system with automatic caching.
+
+The idea is to cache the results of any file system state reads during
+a single transaction. This has two main benefits:
+
+* This avoids redundant syscalls, as we won't perform the same OS
+  operations multiple times.
+
+* This makes it easier to reason about concurrent FS updates, as different
+  operations targeting the same paths can't report different state during
+  a transaction.
+
+Note that this only deals with reading state, not writing.
+
+Properties maintained by the API:
+
+* The contents of the file are always from the same or later time compared
+  to the reported mtime of the file, even if mtime is queried after reading
+  a file.
+
+* Repeating an operation produces the same result as the first one during
+  a transaction.
+
+* Call flush() to start a new transaction (flush the caches).
+
+The API is a bit limited. It's easy to add new cached operations, however.
+You should perform all file system reads through the API to actually take
+advantage of the benefits.
+"""
+
+from __future__ import annotations
+
+import os
+import stat
+
+from mypy_extensions import mypyc_attr
+
+from mypy.util import hash_digest
+
+
+@mypyc_attr(allow_interpreted_subclasses=True)  # for tests
+class FileSystemCache:
+    def __init__(self) -> None:
+        # The package root is not flushed with the caches.
+        # It is set by set_package_root() below.
+        self.package_root: list[str] = []
+        self.flush()
+
+    def set_package_root(self, package_root: list[str]) -> None:
+        self.package_root = package_root
+
+    def flush(self) -> None:
+        """Start another transaction and empty all caches."""
+        self.stat_or_none_cache: dict[str, os.stat_result | None] = {}
+
+        self.listdir_cache: dict[str, list[str]] = {}
+        self.listdir_error_cache: dict[str, OSError] = {}
+        self.isfile_case_cache: dict[str, bool] = {}
+        self.exists_case_cache: dict[str, bool] = {}
+        self.read_cache: dict[str, bytes] = {}
+        self.read_error_cache: dict[str, Exception] = {}
+        self.hash_cache: dict[str, str] = {}
+        self.fake_package_cache: set[str] = set()
+
+    def stat_or_none(self, path: str) -> os.stat_result | None:
+        if path in self.stat_or_none_cache:
+            return self.stat_or_none_cache[path]
+
+        st = None
+        try:
+            st = os.stat(path)
+        except OSError:
+            if self.init_under_package_root(path):
+                try:
+                    st = self._fake_init(path)
+                except OSError:
+                    pass
+
+        self.stat_or_none_cache[path] = st
+        return st
+
+    def init_under_package_root(self, path: str) -> bool:
+        """Is this path an __init__.py under a package root?
+
+        This is used to detect packages that don't contain __init__.py
+        files, which is needed to support Bazel.  The function should
+        only be called for non-existing files.
+
+        It will return True if it refers to a __init__.py file that
+        Bazel would create, so that at runtime Python would think the
+        directory containing it is a package.  For this to work you
+        must pass one or more package roots using the --package-root
+        flag.
+
+        As an exceptional case, any directory that is a package root
+        itself will not be considered to contain a __init__.py file.
+        This is different from the rules Bazel itself applies, but is
+        necessary for mypy to properly distinguish packages from other
+        directories.
+
+        See https://docs.bazel.build/versions/master/be/python.html,
+        where this behavior is described under legacy_create_init.
+        """
+        if not self.package_root:
+            return False
+        dirname, basename = os.path.split(path)
+        if basename != "__init__.py":
+            return False
+        if not os.path.basename(dirname).isidentifier():
+            # Can't put an __init__.py in a place that's not an identifier
+            return False
+
+        st = self.stat_or_none(dirname)
+        if st is None:
+            return False
+        else:
+            if not stat.S_ISDIR(st.st_mode):
+                return False
+        ok = False
+
+        # skip if on a different drive
+        current_drive, _ = os.path.splitdrive(os.getcwd())
+        drive, _ = os.path.splitdrive(path)
+        if drive != current_drive:
+            return False
+        if os.path.isabs(path):
+            path = os.path.relpath(path)
+        path = os.path.normpath(path)
+        for root in self.package_root:
+            if path.startswith(root):
+                if path == root + basename:
+                    # A package root itself is never a package.
+                    ok = False
+                    break
+                else:
+                    ok = True
+        return ok
+
+    def _fake_init(self, path: str) -> os.stat_result:
+        """Prime the cache with a fake __init__.py file.
+
+        This makes code that looks for path believe an empty file by
+        that name exists.  Should only be called after
+        init_under_package_root() returns True.
+        """
+        dirname, basename = os.path.split(path)
+        assert basename == "__init__.py", path
+        assert not os.path.exists(path), path  # Not cached!
+        dirname = os.path.normpath(dirname)
+        st = os.stat(dirname)  # May raise OSError
+        # Get stat result as a list so we can modify it.
+        seq: list[float] = list(st)
+        seq[stat.ST_MODE] = stat.S_IFREG | 0o444
+        seq[stat.ST_INO] = 1
+        seq[stat.ST_NLINK] = 1
+        seq[stat.ST_SIZE] = 0
+        st = os.stat_result(seq)
+        # Make listdir() and read() also pretend this file exists.
+        self.fake_package_cache.add(dirname)
+        return st
+
+    def listdir(self, path: str) -> list[str]:
+        path = os.path.normpath(path)
+        if path in self.listdir_cache:
+            res = self.listdir_cache[path]
+            # Check the fake cache.
+            if path in self.fake_package_cache and "__init__.py" not in res:
+                res.append("__init__.py")  # Updates the result as well as the cache
+            return res
+        if path in self.listdir_error_cache:
+            raise copy_os_error(self.listdir_error_cache[path])
+        try:
+            results = os.listdir(path)
+        except OSError as err:
+            # Like above, take a copy to reduce memory use.
+            self.listdir_error_cache[path] = copy_os_error(err)
+            raise err
+        self.listdir_cache[path] = results
+        # Check the fake cache.
+        if path in self.fake_package_cache and "__init__.py" not in results:
+            results.append("__init__.py")
+        return results
+
+    def isfile(self, path: str) -> bool:
+        st = self.stat_or_none(path)
+        if st is None:
+            return False
+        return stat.S_ISREG(st.st_mode)
+
+    def isfile_case(self, path: str, prefix: str) -> bool:
+        """Return whether path exists and is a file.
+
+        On case-insensitive filesystems (like Mac or Windows) this returns
+        False if the case of path's last component does not exactly match
+        the case found in the filesystem.
+
+        We check also the case of other path components up to prefix.
+        For example, if path is 'user-stubs/pack/mod.pyi' and prefix is 'user-stubs',
+        we check that the case of 'pack' and 'mod.py' matches exactly, 'user-stubs' will be
+        case insensitive on case insensitive filesystems.
+
+        The caller must ensure that prefix is a valid file system prefix of path.
+        """
+        if not self.isfile(path):
+            # Fast path
+            return False
+        if path in self.isfile_case_cache:
+            return self.isfile_case_cache[path]
+        head, tail = os.path.split(path)
+        if not tail:
+            self.isfile_case_cache[path] = False
+            return False
+        try:
+            names = self.listdir(head)
+            # This allows one to check file name case sensitively in
+            # case-insensitive filesystems.
+            res = tail in names
+        except OSError:
+            res = False
+        if res:
+            # Also recursively check the other path components in case sensitive way.
+            res = self.exists_case(head, prefix)
+        self.isfile_case_cache[path] = res
+        return res
+
+    def exists_case(self, path: str, prefix: str) -> bool:
+        """Return whether path exists - checking path components in case sensitive
+        fashion, up to prefix.
+        """
+        if path in self.exists_case_cache:
+            return self.exists_case_cache[path]
+        head, tail = os.path.split(path)
+        if not head.startswith(prefix) or not tail:
+            # Only perform the check for paths under prefix.
+            self.exists_case_cache[path] = True
+            return True
+        try:
+            names = self.listdir(head)
+            # This allows one to check file name case sensitively in
+            # case-insensitive filesystems.
+            res = tail in names
+        except OSError:
+            res = False
+        if res:
+            # Also recursively check other path components.
+            res = self.exists_case(head, prefix)
+        self.exists_case_cache[path] = res
+        return res
+
+    def isdir(self, path: str) -> bool:
+        st = self.stat_or_none(path)
+        if st is None:
+            return False
+        return stat.S_ISDIR(st.st_mode)
+
+    def exists(self, path: str) -> bool:
+        st = self.stat_or_none(path)
+        return st is not None
+
+    def read(self, path: str) -> bytes:
+        if path in self.read_cache:
+            return self.read_cache[path]
+        if path in self.read_error_cache:
+            raise self.read_error_cache[path]
+
+        # Need to stat first so that the contents of file are from no
+        # earlier instant than the mtime reported by self.stat().
+        self.stat_or_none(path)
+
+        dirname, basename = os.path.split(path)
+        dirname = os.path.normpath(dirname)
+        # Check the fake cache.
+        if basename == "__init__.py" and dirname in self.fake_package_cache:
+            data = b""
+        else:
+            try:
+                with open(path, "rb") as f:
+                    data = f.read()
+            except OSError as err:
+                self.read_error_cache[path] = err
+                raise
+
+        self.read_cache[path] = data
+        self.hash_cache[path] = hash_digest(data)
+        return data
+
+    def hash_digest(self, path: str) -> str:
+        if path not in self.hash_cache:
+            self.read(path)
+        return self.hash_cache[path]
+
+    def samefile(self, f1: str, f2: str) -> bool:
+        s1 = self.stat_or_none(f1)
+        s2 = self.stat_or_none(f2)
+        if s1 is None or s2 is None:
+            return False
+        return os.path.samestat(s1, s2)
+
+
+def copy_os_error(e: OSError) -> OSError:
+    new = OSError(*e.args)
+    new.errno = e.errno
+    new.strerror = e.strerror
+    new.filename = e.filename
+    if e.filename2:
+        new.filename2 = e.filename2
+    return new

venv/lib/python3.11/site-packages/mypy/fswatcher.py

@@ -0,0 +1,106 @@
+"""Watch parts of the file system for changes."""
+
+from __future__ import annotations
+
+import os
+from collections.abc import Iterable, Set as AbstractSet
+from typing import NamedTuple
+
+from mypy.fscache import FileSystemCache
+
+
+class FileData(NamedTuple):
+    st_mtime: float
+    st_size: int
+    hash: str
+
+
+class FileSystemWatcher:
+    """Watcher for file system changes among specific paths.
+
+    All file system access is performed using FileSystemCache. We
+    detect changed files by stat()ing them all and comparing hashes
+    of potentially changed files. If a file has both size and mtime
+    unmodified, the file is assumed to be unchanged.
+
+    An important goal of this class is to make it easier to eventually
+    use file system events to detect file changes.
+
+    Note: This class doesn't flush the file system cache. If you don't
+    manually flush it, changes won't be seen.
+    """
+
+    # TODO: Watching directories?
+    # TODO: Handle non-files
+
+    def __init__(self, fs: FileSystemCache) -> None:
+        self.fs = fs
+        self._paths: set[str] = set()
+        self._file_data: dict[str, FileData | None] = {}
+
+    def dump_file_data(self) -> dict[str, tuple[float, int, str]]:
+        return {k: v for k, v in self._file_data.items() if v is not None}
+
+    def set_file_data(self, path: str, data: FileData) -> None:
+        self._file_data[path] = data
+
+    def add_watched_paths(self, paths: Iterable[str]) -> None:
+        for path in paths:
+            if path not in self._paths:
+                # By storing None this path will get reported as changed by
+                # find_changed if it exists.
+                self._file_data[path] = None
+        self._paths |= set(paths)
+
+    def remove_watched_paths(self, paths: Iterable[str]) -> None:
+        for path in paths:
+            if path in self._file_data:
+                del self._file_data[path]
+        self._paths -= set(paths)
+
+    def _update(self, path: str, st: os.stat_result) -> None:
+        hash_digest = self.fs.hash_digest(path)
+        self._file_data[path] = FileData(st.st_mtime, st.st_size, hash_digest)
+
+    def _find_changed(self, paths: Iterable[str]) -> AbstractSet[str]:
+        changed = set()
+        for path in paths:
+            old = self._file_data[path]
+            st = self.fs.stat_or_none(path)
+            if st is None:
+                if old is not None:
+                    # File was deleted.
+                    changed.add(path)
+                    self._file_data[path] = None
+            else:
+                if old is None:
+                    # File is new.
+                    changed.add(path)
+                    self._update(path, st)
+                # Round mtimes down, to match the mtimes we write to meta files
+                elif st.st_size != old.st_size or int(st.st_mtime) != int(old.st_mtime):
+                    # Only look for changes if size or mtime has changed as an
+                    # optimization, since calculating hash is expensive.
+                    new_hash = self.fs.hash_digest(path)
+                    self._update(path, st)
+                    if st.st_size != old.st_size or new_hash != old.hash:
+                        # Changed file.
+                        changed.add(path)
+        return changed
+
+    def find_changed(self) -> AbstractSet[str]:
+        """Return paths that have changes since the last call, in the watched set."""
+        return self._find_changed(self._paths)
+
+    def update_changed(self, remove: list[str], update: list[str]) -> AbstractSet[str]:
+        """Alternative to find_changed() given explicit changes.
+
+        This only calls self.fs.stat() on added or updated files, not
+        on all files.  It believes all other files are unchanged!
+
+        Implies add_watched_paths() for add and update, and
+        remove_watched_paths() for remove.
+        """
+        self.remove_watched_paths(remove)
+        self.add_watched_paths(update)
+        return self._find_changed(update)

venv/lib/python3.11/site-packages/mypy/gclogger.py

@@ -0,0 +1,48 @@
+from __future__ import annotations
+
+import gc
+import time
+from collections.abc import Mapping
+
+
+class GcLogger:
+    """Context manager to log GC stats and overall time."""
+
+    def __enter__(self) -> GcLogger:
+        self.gc_start_time: float | None = None
+        self.gc_time = 0.0
+        self.gc_calls = 0
+        self.gc_collected = 0
+        self.gc_uncollectable = 0
+        gc.callbacks.append(self.gc_callback)
+        self.start_time = time.time()
+        return self
+
+    def gc_callback(self, phase: str, info: Mapping[str, int]) -> None:
+        if phase == "start":
+            assert self.gc_start_time is None, "Start phase out of sequence"
+            self.gc_start_time = time.time()
+        elif phase == "stop":
+            assert self.gc_start_time is not None, "Stop phase out of sequence"
+            self.gc_calls += 1
+            self.gc_time += time.time() - self.gc_start_time
+            self.gc_start_time = None
+            self.gc_collected += info["collected"]
+            self.gc_uncollectable += info["uncollectable"]
+        else:
+            assert False, f"Unrecognized gc phase ({phase!r})"
+
+    def __exit__(self, *args: object) -> None:
+        while self.gc_callback in gc.callbacks:
+            gc.callbacks.remove(self.gc_callback)
+
+    def get_stats(self) -> Mapping[str, float]:
+        end_time = time.time()
+        result = {
+            "gc_time": self.gc_time,
+            "gc_calls": self.gc_calls,
+            "gc_collected": self.gc_collected,
+            "gc_uncollectable": self.gc_uncollectable,
+            "build_time": end_time - self.start_time,
+        }
+        return result

venv/lib/python3.11/site-packages/mypy/git.py

@@ -0,0 +1,34 @@
+"""Git utilities."""
+
+# Used also from setup.py, so don't pull in anything additional here (like mypy or typing):
+from __future__ import annotations
+
+import os
+import subprocess
+
+
+def is_git_repo(dir: str) -> bool:
+    """Is the given directory version-controlled with git?"""
+    return os.path.exists(os.path.join(dir, ".git"))
+
+
+def have_git() -> bool:
+    """Can we run the git executable?"""
+    try:
+        subprocess.check_output(["git", "--help"])
+        return True
+    except subprocess.CalledProcessError:
+        return False
+    except OSError:
+        return False
+
+
+def git_revision(dir: str) -> bytes:
+    """Get the SHA-1 of the HEAD of a git repository."""
+    return subprocess.check_output(["git", "rev-parse", "HEAD"], cwd=dir).strip()
+
+
+def is_dirty(dir: str) -> bool:
+    """Check whether a git repository has uncommitted changes."""
+    output = subprocess.check_output(["git", "status", "-uno", "--porcelain"], cwd=dir)
+    return output.strip() != b""

venv/lib/python3.11/site-packages/mypy/graph_utils.py

@@ -0,0 +1,161 @@
+"""Helpers for manipulations with graphs."""
+
+from __future__ import annotations
+
+from collections.abc import Iterator, Set as AbstractSet
+from typing import TypeVar
+
+T = TypeVar("T")
+
+
+def strongly_connected_components(
+    vertices: AbstractSet[T], edges: dict[T, list[T]]
+) -> Iterator[set[T]]:
+    """Compute Strongly Connected Components of a directed graph.
+
+    Args:
+      vertices: the labels for the vertices
+      edges: for each vertex, gives the target vertices of its outgoing edges
+
+    Returns:
+      An iterator yielding strongly connected components, each
+      represented as a set of vertices.  Each input vertex will occur
+      exactly once; vertices not part of a SCC are returned as
+      singleton sets.
+
+    From https://code.activestate.com/recipes/578507/.
+    """
+    identified: set[T] = set()
+    stack: list[T] = []
+    index: dict[T, int] = {}
+    boundaries: list[int] = []
+
+    def dfs(v: T) -> Iterator[set[T]]:
+        index[v] = len(stack)
+        stack.append(v)
+        boundaries.append(index[v])
+
+        for w in edges[v]:
+            if w not in index:
+                yield from dfs(w)
+            elif w not in identified:
+                while index[w] < boundaries[-1]:
+                    boundaries.pop()
+
+        if boundaries[-1] == index[v]:
+            boundaries.pop()
+            scc = set(stack[index[v] :])
+            del stack[index[v] :]
+            identified.update(scc)
+            yield scc
+
+    for v in vertices:
+        if v not in index:
+            yield from dfs(v)
+
+
+def prepare_sccs(
+    sccs: list[set[T]], edges: dict[T, list[T]]
+) -> dict[AbstractSet[T], set[AbstractSet[T]]]:
+    """Use original edges to organize SCCs in a graph by dependencies between them."""
+    sccsmap = {}
+    for scc in sccs:
+        scc_frozen = frozenset(scc)
+        for v in scc:
+            sccsmap[v] = scc_frozen
+    data: dict[AbstractSet[T], set[AbstractSet[T]]] = {}
+    for scc in sccs:
+        deps: set[AbstractSet[T]] = set()
+        for v in scc:
+            deps.update(sccsmap[x] for x in edges[v])
+        data[frozenset(scc)] = deps
+    return data
+
+
+class topsort(Iterator[set[T]]):  # noqa: N801
+    """Topological sort using Kahn's algorithm.
+
+    Uses in-degree counters and a reverse adjacency list, so the total work
+    is O(V + E).
+
+    Implemented as a class rather than a generator for better mypyc
+    compilation.
+
+    Args:
+      data: A map from vertices to all vertices that it has an edge
+            connecting it to. NOTE: dependency sets in this data
+            structure are modified in place to remove self-dependencies.
+            Orphans are handled internally and are not added to `data`.
+
+    Returns:
+      An iterator yielding sets of vertices that have an equivalent
+      ordering.
+
+    Example:
+      Suppose the input has the following structure:
+
+        {A: {B, C}, B: {D}, C: {D}}
+
+      The algorithm treats orphan dependencies as if normalized to:
+
+        {A: {B, C}, B: {D}, C: {D}, D: {}}
+
+      It will yield the following values:
+
+        {D}
+        {B, C}
+        {A}
+    """
+
+    def __init__(self, data: dict[T, set[T]]) -> None:
+        # Single pass: remove self-deps, build reverse adjacency list,
+        # compute in-degree counts, detect orphans, and find initial ready set.
+        in_degree: dict[T, int] = {}
+        rev: dict[T, list[T]] = {}
+        ready: set[T] = set()
+        for item, deps in data.items():
+            deps.discard(item)  # Ignore self dependencies.
+            deg = len(deps)
+            in_degree[item] = deg
+            if deg == 0:
+                ready.add(item)
+            if item not in rev:
+                rev[item] = []
+            for dep in deps:
+                if dep in rev:
+                    rev[dep].append(item)
+                else:
+                    rev[dep] = [item]
+                    if dep not in data:
+                        # Orphan: appears as dependency but has no entry in data.
+                        in_degree[dep] = 0
+                        ready.add(dep)
+
+        self.in_degree = in_degree
+        self.rev = rev
+        self.ready = ready
+        self.remaining = len(in_degree) - len(ready)
+
+    def __iter__(self) -> Iterator[set[T]]:
+        return self
+
+    def __next__(self) -> set[T]:
+        ready = self.ready
+        if not ready:
+            assert self.remaining == 0, (
+                f"A cyclic dependency exists amongst "
+                f"{[k for k, deg in self.in_degree.items() if deg > 0]!r}"
+            )
+            raise StopIteration
+        in_degree = self.in_degree
+        rev = self.rev
+        new_ready: set[T] = set()
+        for item in ready:
+            for dependent in rev[item]:
+                new_deg = in_degree[dependent] - 1
+                in_degree[dependent] = new_deg
+                if new_deg == 0:
+                    new_ready.add(dependent)
+        self.remaining -= len(new_ready)
+        self.ready = new_ready
+        return ready

venv/lib/python3.11/site-packages/mypy/indirection.py

@@ -0,0 +1,170 @@
+from __future__ import annotations
+
+from collections.abc import Iterable
+
+import mypy.types as types
+from mypy.types import TypeVisitor
+
+
+class TypeIndirectionVisitor(TypeVisitor[None]):
+    """Returns all module references within a particular type."""
+
+    def __init__(self) -> None:
+        # Module references are collected here
+        self.modules: set[str] = set()
+        # User to avoid infinite recursion with recursive types
+        self.seen_types: set[types.TypeAliasType | types.Instance] = set()
+
+    def find_modules(self, typs: Iterable[types.Type]) -> set[str]:
+        self.modules = set()
+        self.seen_types = set()
+        for typ in typs:
+            self._visit(typ)
+        return self.modules
+
+    def _visit(self, typ: types.Type) -> None:
+        # Note: instances are needed for `class str(Sequence[str]): ...`
+        if (
+            isinstance(typ, types.TypeAliasType)
+            or isinstance(typ, types.ProperType)
+            and isinstance(typ, types.Instance)
+        ):
+            # Avoid infinite recursion for recursive types.
+            if typ in self.seen_types:
+                return
+            self.seen_types.add(typ)
+        typ.accept(self)
+
+    def _visit_type_tuple(self, typs: tuple[types.Type, ...]) -> None:
+        # Micro-optimization: Specialized version of _visit for lists
+        for typ in typs:
+            if (
+                isinstance(typ, types.TypeAliasType)
+                or isinstance(typ, types.ProperType)
+                and isinstance(typ, types.Instance)
+            ):
+                # Avoid infinite recursion for recursive types.
+                if typ in self.seen_types:
+                    continue
+                self.seen_types.add(typ)
+            typ.accept(self)
+
+    def _visit_type_list(self, typs: list[types.Type]) -> None:
+        # Micro-optimization: Specialized version of _visit for tuples
+        for typ in typs:
+            if (
+                isinstance(typ, types.TypeAliasType)
+                or isinstance(typ, types.ProperType)
+                and isinstance(typ, types.Instance)
+            ):
+                # Avoid infinite recursion for recursive types.
+                if typ in self.seen_types:
+                    continue
+                self.seen_types.add(typ)
+            typ.accept(self)
+
+    def visit_unbound_type(self, t: types.UnboundType) -> None:
+        self._visit_type_tuple(t.args)
+
+    def visit_any(self, t: types.AnyType) -> None:
+        pass
+
+    def visit_none_type(self, t: types.NoneType) -> None:
+        pass
+
+    def visit_uninhabited_type(self, t: types.UninhabitedType) -> None:
+        pass
+
+    def visit_erased_type(self, t: types.ErasedType) -> None:
+        pass
+
+    def visit_deleted_type(self, t: types.DeletedType) -> None:
+        pass
+
+    def visit_type_var(self, t: types.TypeVarType) -> None:
+        self._visit_type_list(t.values)
+        self._visit(t.upper_bound)
+        self._visit(t.default)
+
+    def visit_param_spec(self, t: types.ParamSpecType) -> None:
+        self._visit(t.upper_bound)
+        self._visit(t.default)
+        self._visit(t.prefix)
+
+    def visit_type_var_tuple(self, t: types.TypeVarTupleType) -> None:
+        self._visit(t.upper_bound)
+        self._visit(t.default)
+
+    def visit_unpack_type(self, t: types.UnpackType) -> None:
+        t.type.accept(self)
+
+    def visit_parameters(self, t: types.Parameters) -> None:
+        self._visit_type_list(t.arg_types)
+
+    def visit_instance(self, t: types.Instance) -> None:
+        # Instance is named, record its definition and continue digging into
+        # components that constitute semantic meaning of this type: bases, metaclass,
+        # tuple type, and typeddict type.
+        # Note: we cannot simply record the MRO, in case an intermediate base contains
+        # a reference to type alias, this affects meaning of map_instance_to_supertype(),
+        # see e.g. testDoubleReexportGenericUpdated.
+        self._visit_type_tuple(t.args)
+        if t.type:
+            # Important optimization: instead of simply recording the definition and
+            # recursing into bases, record the MRO and only traverse generic bases.
+            for s in t.type.mro:
+                self.modules.add(s.module_name)
+                for base in s.bases:
+                    if base.args:
+                        self._visit_type_tuple(base.args)
+            if t.type.metaclass_type:
+                self._visit(t.type.metaclass_type)
+            if t.type.typeddict_type:
+                self._visit(t.type.typeddict_type)
+            if t.type.tuple_type:
+                self._visit(t.type.tuple_type)
+            if t.type.is_protocol:
+                # For protocols, member types constitute the semantic meaning of the type.
+                # TODO: this doesn't cover some edge cases, like setter types and exotic nodes.
+                for m in t.type.protocol_members:
+                    node = t.type.names.get(m)
+                    if node and node.type:
+                        self._visit(node.type)
+
+    def visit_callable_type(self, t: types.CallableType) -> None:
+        self._visit_type_list(t.arg_types)
+        self._visit(t.ret_type)
+        self._visit_type_tuple(t.variables)
+
+    def visit_overloaded(self, t: types.Overloaded) -> None:
+        for item in t.items:
+            self._visit(item)
+        self._visit(t.fallback)
+
+    def visit_tuple_type(self, t: types.TupleType) -> None:
+        self._visit_type_list(t.items)
+        self._visit(t.partial_fallback)
+
+    def visit_typeddict_type(self, t: types.TypedDictType) -> None:
+        self._visit_type_list(list(t.items.values()))
+        self._visit(t.fallback)
+
+    def visit_literal_type(self, t: types.LiteralType) -> None:
+        self._visit(t.fallback)
+
+    def visit_union_type(self, t: types.UnionType) -> None:
+        self._visit_type_list(t.items)
+
+    def visit_partial_type(self, t: types.PartialType) -> None:
+        pass
+
+    def visit_type_type(self, t: types.TypeType) -> None:
+        self._visit(t.item)
+
+    def visit_type_alias_type(self, t: types.TypeAliasType) -> None:
+        # Type alias is named, record its definition and continue digging into
+        # components that constitute semantic meaning of this type: target and args.
+        if t.alias:
+            self.modules.add(t.alias.module)
+            self._visit(t.alias.target)
+        self._visit_type_list(t.args)

venv/lib/python3.11/site-packages/mypy/infer.py

@@ -0,0 +1,76 @@
+"""Utilities for type argument inference."""
+
+from __future__ import annotations
+
+from collections.abc import Sequence
+from typing import NamedTuple
+
+from mypy.constraints import (
+    SUBTYPE_OF,
+    SUPERTYPE_OF,
+    infer_constraints,
+    infer_constraints_for_callable,
+)
+from mypy.nodes import ArgKind
+from mypy.solve import solve_constraints
+from mypy.types import CallableType, Instance, Type, TypeVarLikeType
+
+
+class ArgumentInferContext(NamedTuple):
+    """Type argument inference context.
+
+    We need this because we pass around ``Mapping`` and ``Iterable`` types.
+    These types are only known by ``TypeChecker`` itself.
+    It is required for ``*`` and ``**`` argument inference.
+
+    https://github.com/python/mypy/issues/11144
+    """
+
+    mapping_type: Instance
+    iterable_type: Instance
+
+
+def infer_function_type_arguments(
+    callee_type: CallableType,
+    arg_types: Sequence[Type | None],
+    arg_kinds: list[ArgKind],
+    arg_names: Sequence[str | None] | None,
+    formal_to_actual: list[list[int]],
+    context: ArgumentInferContext,
+    strict: bool = True,
+    allow_polymorphic: bool = False,
+) -> tuple[list[Type | None], list[TypeVarLikeType]]:
+    """Infer the type arguments of a generic function.
+
+    Return an array of lower bound types for the type variables -1 (at
+    index 0), -2 (at index 1), etc. A lower bound is None if a value
+    could not be inferred.
+
+    Arguments:
+      callee_type: the target generic function
+      arg_types: argument types at the call site (each optional; if None,
+                 we are not considering this argument in the current pass)
+      arg_kinds: nodes.ARG_* values for arg_types
+      formal_to_actual: mapping from formal to actual variable indices
+    """
+    # Infer constraints.
+    constraints = infer_constraints_for_callable(
+        callee_type, arg_types, arg_kinds, arg_names, formal_to_actual, context
+    )
+
+    # Solve constraints.
+    type_vars = callee_type.variables
+    return solve_constraints(type_vars, constraints, strict, allow_polymorphic)
+
+
+def infer_type_arguments(
+    type_vars: Sequence[TypeVarLikeType],
+    template: Type,
+    actual: Type,
+    is_supertype: bool = False,
+    skip_unsatisfied: bool = False,
+) -> list[Type | None]:
+    # Like infer_function_type_arguments, but only match a single type
+    # against a generic type.
+    constraints = infer_constraints(template, actual, SUPERTYPE_OF if is_supertype else SUBTYPE_OF)
+    return solve_constraints(type_vars, constraints, skip_unsatisfied=skip_unsatisfied)[0]

venv/lib/python3.11/site-packages/mypy/inspections.py

@@ -0,0 +1,626 @@
+from __future__ import annotations
+
+import os
+from collections import defaultdict
+from collections.abc import Callable
+from functools import cmp_to_key
+
+from mypy.build import State
+from mypy.messages import format_type
+from mypy.modulefinder import PYTHON_EXTENSIONS
+from mypy.nodes import (
+    LDEF,
+    Decorator,
+    Expression,
+    FuncBase,
+    MemberExpr,
+    MypyFile,
+    Node,
+    OverloadedFuncDef,
+    RefExpr,
+    SymbolNode,
+    TypeInfo,
+    Var,
+)
+from mypy.server.update import FineGrainedBuildManager
+from mypy.traverser import ExtendedTraverserVisitor
+from mypy.typeops import tuple_fallback
+from mypy.types import (
+    FunctionLike,
+    Instance,
+    LiteralType,
+    ProperType,
+    TupleType,
+    TypedDictType,
+    TypeVarType,
+    UnionType,
+    get_proper_type,
+)
+from mypy.typevars import fill_typevars_with_any
+
+
+def node_starts_after(o: Node, line: int, column: int) -> bool:
+    return o.line > line or o.line == line and o.column > column
+
+
+def node_ends_before(o: Node, line: int, column: int) -> bool:
+    # Unfortunately, end positions for some statements are a mess,
+    # e.g. overloaded functions, so we return False when we don't know.
+    if o.end_line is not None and o.end_column is not None:
+        if o.end_line < line or o.end_line == line and o.end_column < column:
+            return True
+    return False
+
+
+def expr_span(expr: Expression) -> str:
+    """Format expression span as in mypy error messages."""
+    return f"{expr.line}:{expr.column + 1}:{expr.end_line}:{expr.end_column}"
+
+
+def get_instance_fallback(typ: ProperType) -> list[Instance]:
+    """Returns the Instance fallback for this type if one exists or None."""
+    if isinstance(typ, Instance):
+        return [typ]
+    elif isinstance(typ, TupleType):
+        return [tuple_fallback(typ)]
+    elif isinstance(typ, TypedDictType):
+        return [typ.fallback]
+    elif isinstance(typ, FunctionLike):
+        return [typ.fallback]
+    elif isinstance(typ, LiteralType):
+        return [typ.fallback]
+    elif isinstance(typ, TypeVarType):
+        if typ.values:
+            res = []
+            for t in typ.values:
+                res.extend(get_instance_fallback(get_proper_type(t)))
+            return res
+        return get_instance_fallback(get_proper_type(typ.upper_bound))
+    elif isinstance(typ, UnionType):
+        res = []
+        for t in typ.items:
+            res.extend(get_instance_fallback(get_proper_type(t)))
+        return res
+    return []
+
+
+def find_node(name: str, info: TypeInfo) -> Var | FuncBase | None:
+    """Find the node defining member 'name' in given TypeInfo."""
+    # TODO: this code shares some logic with checkmember.py
+    method = info.get_method(name)
+    if method:
+        if isinstance(method, Decorator):
+            return method.var
+        if method.is_property:
+            assert isinstance(method, OverloadedFuncDef)
+            dec = method.items[0]
+            assert isinstance(dec, Decorator)
+            return dec.var
+        return method
+    else:
+        # don't have such method, maybe variable?
+        node = info.get(name)
+        v = node.node if node else None
+        if isinstance(v, Var):
+            return v
+    return None
+
+
+def find_module_by_fullname(fullname: str, modules: dict[str, State]) -> State | None:
+    """Find module by a node fullname.
+
+    This logic mimics the one we use in fixup, so should be good enough.
+    """
+    head = fullname
+    # Special case: a module symbol is considered to be defined in itself, not in enclosing
+    # package, since this is what users want when clicking go to definition on a module.
+    if head in modules:
+        return modules[head]
+    while True:
+        if "." not in head:
+            return None
+        head, tail = head.rsplit(".", maxsplit=1)
+        mod = modules.get(head)
+        if mod is not None:
+            return mod
+
+
+class SearchVisitor(ExtendedTraverserVisitor):
+    """Visitor looking for an expression whose span matches given one exactly."""
+
+    def __init__(self, line: int, column: int, end_line: int, end_column: int) -> None:
+        self.line = line
+        self.column = column
+        self.end_line = end_line
+        self.end_column = end_column
+        self.result: Expression | None = None
+
+    def visit(self, o: Node) -> bool:
+        if node_starts_after(o, self.line, self.column):
+            return False
+        if node_ends_before(o, self.end_line, self.end_column):
+            return False
+        if (
+            o.line == self.line
+            and o.end_line == self.end_line
+            and o.column == self.column
+            and o.end_column == self.end_column
+        ):
+            if isinstance(o, Expression):
+                self.result = o
+        return self.result is None
+
+
+def find_by_location(
+    tree: MypyFile, line: int, column: int, end_line: int, end_column: int
+) -> Expression | None:
+    """Find an expression matching given span, or None if not found."""
+    if end_line < line:
+        raise ValueError('"end_line" must not be before "line"')
+    if end_line == line and end_column <= column:
+        raise ValueError('"end_column" must be after "column"')
+    visitor = SearchVisitor(line, column, end_line, end_column)
+    tree.accept(visitor)
+    return visitor.result
+
+
+class SearchAllVisitor(ExtendedTraverserVisitor):
+    """Visitor looking for all expressions whose spans enclose given position."""
+
+    def __init__(self, line: int, column: int) -> None:
+        self.line = line
+        self.column = column
+        self.result: list[Expression] = []
+
+    def visit(self, o: Node) -> bool:
+        if node_starts_after(o, self.line, self.column):
+            return False
+        if node_ends_before(o, self.line, self.column):
+            return False
+        if isinstance(o, Expression):
+            self.result.append(o)
+        return True
+
+
+def find_all_by_location(tree: MypyFile, line: int, column: int) -> list[Expression]:
+    """Find all expressions enclosing given position starting from innermost."""
+    visitor = SearchAllVisitor(line, column)
+    tree.accept(visitor)
+    return list(reversed(visitor.result))
+
+
+class InspectionEngine:
+    """Engine for locating and statically inspecting expressions."""
+
+    def __init__(
+        self,
+        fg_manager: FineGrainedBuildManager,
+        *,
+        verbosity: int = 0,
+        limit: int = 0,
+        include_span: bool = False,
+        include_kind: bool = False,
+        include_object_attrs: bool = False,
+        union_attrs: bool = False,
+        force_reload: bool = False,
+    ) -> None:
+        self.fg_manager = fg_manager
+        self.verbosity = verbosity
+        self.limit = limit
+        self.include_span = include_span
+        self.include_kind = include_kind
+        self.include_object_attrs = include_object_attrs
+        self.union_attrs = union_attrs
+        self.force_reload = force_reload
+        # Module for which inspection was requested.
+        self.module: State | None = None
+
+    def reload_module(self, state: State) -> None:
+        """Reload given module while temporary exporting types."""
+        old = self.fg_manager.manager.options.export_types
+        self.fg_manager.manager.options.export_types = True
+        try:
+            self.fg_manager.flush_cache()
+            assert state.path is not None
+            self.fg_manager.update([(state.id, state.path)], [])
+        finally:
+            self.fg_manager.manager.options.export_types = old
+
+    def expr_type(self, expression: Expression) -> tuple[str, bool]:
+        """Format type for an expression using current options.
+
+        If type is known, second item returned is True. If type is not known, an error
+        message is returned instead, and second item returned is False.
+        """
+        expr_type = self.fg_manager.manager.all_types.get(expression)
+        if expr_type is None:
+            return self.missing_type(expression), False
+
+        type_str = format_type(
+            expr_type, self.fg_manager.manager.options, verbosity=self.verbosity
+        )
+        return self.add_prefixes(type_str, expression), True
+
+    def object_type(self) -> Instance:
+        builtins = self.fg_manager.graph["builtins"].tree
+        assert builtins is not None
+        object_node = builtins.names["object"].node
+        assert isinstance(object_node, TypeInfo)
+        return Instance(object_node, [])
+
+    def collect_attrs(self, instances: list[Instance]) -> dict[TypeInfo, list[str]]:
+        """Collect attributes from all union/typevar variants."""
+
+        def item_attrs(attr_dict: dict[TypeInfo, list[str]]) -> set[str]:
+            attrs = set()
+            for base in attr_dict:
+                attrs |= set(attr_dict[base])
+            return attrs
+
+        def cmp_types(x: TypeInfo, y: TypeInfo) -> int:
+            if x in y.mro:
+                return 1
+            if y in x.mro:
+                return -1
+            return 0
+
+        # First gather all attributes for every union variant.
+        assert instances
+        all_attrs = []
+        for instance in instances:
+            attrs = {}
+            mro = instance.type.mro
+            if not self.include_object_attrs:
+                mro = mro[:-1]
+            for base in mro:
+                attrs[base] = sorted(base.names)
+            all_attrs.append(attrs)
+
+        # Find attributes valid for all variants in a union or type variable.
+        intersection = item_attrs(all_attrs[0])
+        for item in all_attrs[1:]:
+            intersection &= item_attrs(item)
+
+        # Combine attributes from all variants into a single dict while
+        # also removing invalid attributes (unless using --union-attrs).
+        combined_attrs = defaultdict(list)
+        for item in all_attrs:
+            for base in item:
+                if base in combined_attrs:
+                    continue
+                for name in item[base]:
+                    if self.union_attrs or name in intersection:
+                        combined_attrs[base].append(name)
+
+        # Sort bases by MRO, unrelated will appear in the order they appeared as union variants.
+        sorted_bases = sorted(combined_attrs.keys(), key=cmp_to_key(cmp_types))
+        result = {}
+        for base in sorted_bases:
+            if not combined_attrs[base]:
+                # Skip bases where everytihng was filtered out.
+                continue
+            result[base] = combined_attrs[base]
+        return result
+
+    def _fill_from_dict(
+        self, attrs_strs: list[str], attrs_dict: dict[TypeInfo, list[str]]
+    ) -> None:
+        for base in attrs_dict:
+            cls_name = base.name if self.verbosity < 1 else base.fullname
+            attrs = [f'"{attr}"' for attr in attrs_dict[base]]
+            attrs_strs.append(f'"{cls_name}": [{", ".join(attrs)}]')
+
+    def expr_attrs(self, expression: Expression) -> tuple[str, bool]:
+        """Format attributes that are valid for a given expression.
+
+        If expression type is not an Instance, try using fallback. Attributes are
+        returned as a JSON (ordered by MRO) that maps base class name to list of
+        attributes. Attributes may appear in multiple bases if overridden (we simply
+        follow usual mypy logic for creating new Vars etc).
+        """
+        expr_type = self.fg_manager.manager.all_types.get(expression)
+        if expr_type is None:
+            return self.missing_type(expression), False
+
+        expr_type = get_proper_type(expr_type)
+        instances = get_instance_fallback(expr_type)
+        if not instances:
+            # Everything is an object in Python.
+            instances = [self.object_type()]
+
+        attrs_dict = self.collect_attrs(instances)
+
+        # Special case: modules have names apart from those from ModuleType.
+        if isinstance(expression, RefExpr) and isinstance(expression.node, MypyFile):
+            node = expression.node
+            names = sorted(node.names)
+            if "__builtins__" in names:
+                # This is just to make tests stable. No one will really need this name.
+                names.remove("__builtins__")
+            mod_dict = {f'"<{node.fullname}>"': [f'"{name}"' for name in names]}
+        else:
+            mod_dict = {}
+
+        # Special case: for class callables, prepend with the class attributes.
+        # TODO: also handle cases when such callable appears in a union.
+        if isinstance(expr_type, FunctionLike) and expr_type.is_type_obj():
+            template = fill_typevars_with_any(expr_type.type_object())
+            class_dict = self.collect_attrs(get_instance_fallback(template))
+        else:
+            class_dict = {}
+
+        # We don't use JSON dump to be sure keys order is always preserved.
+        base_attrs = []
+        if mod_dict:
+            for mod in mod_dict:
+                base_attrs.append(f'{mod}: [{", ".join(mod_dict[mod])}]')
+        self._fill_from_dict(base_attrs, class_dict)
+        self._fill_from_dict(base_attrs, attrs_dict)
+        return self.add_prefixes(f'{{{", ".join(base_attrs)}}}', expression), True
+
+    def format_node(self, module: State, node: FuncBase | SymbolNode) -> str:
+        return f"{module.path}:{node.line}:{node.column + 1}:{node.name}"
+
+    def collect_nodes(self, expression: RefExpr) -> list[FuncBase | SymbolNode]:
+        """Collect nodes that can be referred to by an expression.
+
+        Note: it can be more than one for example in case of a union attribute.
+        """
+        node: FuncBase | SymbolNode | None = expression.node
+        nodes: list[FuncBase | SymbolNode]
+        if node is None:
+            # Tricky case: instance attribute
+            if isinstance(expression, MemberExpr) and expression.kind is None:
+                base_type = self.fg_manager.manager.all_types.get(expression.expr)
+                if base_type is None:
+                    return []
+
+                # Now we use the base type to figure out where the attribute is defined.
+                base_type = get_proper_type(base_type)
+                instances = get_instance_fallback(base_type)
+                nodes = []
+                for instance in instances:
+                    node = find_node(expression.name, instance.type)
+                    if node:
+                        nodes.append(node)
+                if not nodes:
+                    # Try checking class namespace if attribute is on a class object.
+                    if isinstance(base_type, FunctionLike) and base_type.is_type_obj():
+                        instances = get_instance_fallback(
+                            fill_typevars_with_any(base_type.type_object())
+                        )
+                        for instance in instances:
+                            node = find_node(expression.name, instance.type)
+                            if node:
+                                nodes.append(node)
+                    else:
+                        # Still no luck, give up.
+                        return []
+            else:
+                return []
+        else:
+            # Easy case: a module-level definition
+            nodes = [node]
+        return nodes
+
+    def modules_for_nodes(
+        self, nodes: list[FuncBase | SymbolNode], expression: RefExpr
+    ) -> tuple[dict[FuncBase | SymbolNode, State], bool]:
+        """Gather modules where given nodes where defined.
+
+        Also check if they need to be refreshed (cached nodes may have
+        lines/columns missing).
+        """
+        modules = {}
+        reload_needed = False
+        for node in nodes:
+            module = find_module_by_fullname(node.fullname, self.fg_manager.graph)
+            if not module:
+                if expression.kind == LDEF and self.module:
+                    module = self.module
+                else:
+                    continue
+            modules[node] = module
+            if not module.tree or module.tree.is_cache_skeleton or self.force_reload:
+                reload_needed |= not module.tree or module.tree.is_cache_skeleton
+                self.reload_module(module)
+        return modules, reload_needed
+
+    def expression_def(self, expression: Expression) -> tuple[str, bool]:
+        """Find and format definition location for an expression.
+
+        If it is not a RefExpr, it is effectively skipped by returning an
+        empty result.
+        """
+        if not isinstance(expression, RefExpr):
+            # If there are no suitable matches at all, we return error later.
+            return "", True
+
+        nodes = self.collect_nodes(expression)
+
+        if not nodes:
+            return self.missing_node(expression), False
+
+        modules, reload_needed = self.modules_for_nodes(nodes, expression)
+        if reload_needed:
+            # TODO: line/column are not stored in cache for vast majority of symbol nodes.
+            # Adding them will make thing faster, but will have visible memory impact.
+            nodes = self.collect_nodes(expression)
+            modules, reload_needed = self.modules_for_nodes(nodes, expression)
+            assert not reload_needed
+
+        result = []
+        for node in modules:
+            result.append(self.format_node(modules[node], node))
+
+        if not result:
+            return self.missing_node(expression), False
+
+        return self.add_prefixes(", ".join(result), expression), True
+
+    def missing_type(self, expression: Expression) -> str:
+        alt_suggestion = ""
+        if not self.force_reload:
+            alt_suggestion = " or try --force-reload"
+        return (
+            f'No known type available for "{type(expression).__name__}"'
+            f" (maybe unreachable{alt_suggestion})"
+        )
+
+    def missing_node(self, expression: Expression) -> str:
+        return (
+            f'Cannot find definition for "{type(expression).__name__}" at {expr_span(expression)}'
+        )
+
+    def add_prefixes(self, result: str, expression: Expression) -> str:
+        prefixes = []
+        if self.include_kind:
+            prefixes.append(f"{type(expression).__name__}")
+        if self.include_span:
+            prefixes.append(expr_span(expression))
+        if prefixes:
+            prefix = ":".join(prefixes) + " -> "
+        else:
+            prefix = ""
+        return prefix + result
+
+    def run_inspection_by_exact_location(
+        self,
+        tree: MypyFile,
+        line: int,
+        column: int,
+        end_line: int,
+        end_column: int,
+        method: Callable[[Expression], tuple[str, bool]],
+    ) -> dict[str, object]:
+        """Get type of an expression matching a span.
+
+        Type or error is returned as a standard daemon response dict.
+        """
+        try:
+            expression = find_by_location(tree, line, column - 1, end_line, end_column)
+        except ValueError as err:
+            return {"error": str(err)}
+
+        if expression is None:
+            span = f"{line}:{column}:{end_line}:{end_column}"
+            return {"out": f"Can't find expression at span {span}", "err": "", "status": 1}
+
+        inspection_str, success = method(expression)
+        return {"out": inspection_str, "err": "", "status": 0 if success else 1}
+
+    def run_inspection_by_position(
+        self,
+        tree: MypyFile,
+        line: int,
+        column: int,
+        method: Callable[[Expression], tuple[str, bool]],
+    ) -> dict[str, object]:
+        """Get types of all expressions enclosing a position.
+
+        Types and/or errors are returned as a standard daemon response dict.
+        """
+        expressions = find_all_by_location(tree, line, column - 1)
+        if not expressions:
+            position = f"{line}:{column}"
+            return {
+                "out": f"Can't find any expressions at position {position}",
+                "err": "",
+                "status": 1,
+            }
+
+        inspection_strs = []
+        status = 0
+        for expression in expressions:
+            inspection_str, success = method(expression)
+            if not success:
+                status = 1
+            if inspection_str:
+                inspection_strs.append(inspection_str)
+        if self.limit:
+            inspection_strs = inspection_strs[: self.limit]
+        return {"out": "\n".join(inspection_strs), "err": "", "status": status}
+
+    def find_module(self, file: str) -> tuple[State | None, dict[str, object]]:
+        """Find module by path, or return a suitable error message.
+
+        Note we don't use exceptions to simplify handling 1 vs 2 statuses.
+        """
+        if not any(file.endswith(ext) for ext in PYTHON_EXTENSIONS):
+            return None, {"error": "Source file is not a Python file"}
+
+        # We are using a bit slower but robust way to find a module by path,
+        # to be sure that namespace packages are handled properly.
+        abs_path = os.path.abspath(file)
+        state = next((s for s in self.fg_manager.graph.values() if s.abspath == abs_path), None)
+        self.module = state
+        return (
+            state,
+            {"out": f"Unknown module: {file}", "err": "", "status": 1} if state is None else {},
+        )
+
+    def run_inspection(
+        self, location: str, method: Callable[[Expression], tuple[str, bool]]
+    ) -> dict[str, object]:
+        """Top-level logic to inspect expression(s) at a location.
+
+        This can be reused by various simple inspections.
+        """
+        try:
+            file, pos = parse_location(location)
+        except ValueError as err:
+            return {"error": str(err)}
+
+        state, err_dict = self.find_module(file)
+        if state is None:
+            assert err_dict
+            return err_dict
+
+        # Force reloading to load from cache, account for any edits, etc.
+        if not state.tree or state.tree.is_cache_skeleton or self.force_reload:
+            self.reload_module(state)
+        assert state.tree is not None
+
+        if len(pos) == 4:
+            # Full span, return an exact match only.
+            line, column, end_line, end_column = pos
+            return self.run_inspection_by_exact_location(
+                state.tree, line, column, end_line, end_column, method
+            )
+        assert len(pos) == 2
+        # Inexact location, return all expressions.
+        line, column = pos
+        return self.run_inspection_by_position(state.tree, line, column, method)
+
+    def get_type(self, location: str) -> dict[str, object]:
+        """Get types of expression(s) at a location."""
+        return self.run_inspection(location, self.expr_type)
+
+    def get_attrs(self, location: str) -> dict[str, object]:
+        """Get attributes of expression(s) at a location."""
+        return self.run_inspection(location, self.expr_attrs)
+
+    def get_definition(self, location: str) -> dict[str, object]:
+        """Get symbol definitions of expression(s) at a location."""
+        result = self.run_inspection(location, self.expression_def)
+        if "out" in result and not result["out"]:
+            # None of the expressions found turns out to be a RefExpr.
+            _, location = location.split(":", maxsplit=1)
+            result["out"] = f"No name or member expressions at {location}"
+            result["status"] = 1
+        return result
+
+
+def parse_location(location: str) -> tuple[str, list[int]]:
+    if location.count(":") < 2:
+        raise ValueError("Format should be file:line:column[:end_line:end_column]")
+    parts = location.rsplit(":", maxsplit=2)
+    start, *rest = parts
+    # Note: we must allow drive prefix like `C:` on Windows.
+    if start.count(":") < 2:
+        return start, [int(p) for p in rest]
+    parts = start.rsplit(":", maxsplit=2)
+    start, *start_rest = parts
+    if start.count(":") < 2:
+        return start, [int(p) for p in start_rest + rest]
+    raise ValueError("Format should be file:line:column[:end_line:end_column]")

venv/lib/python3.11/site-packages/mypy/ipc.py

@@ -0,0 +1,457 @@
+"""Cross-platform abstractions for inter-process communication
+
+On Unix, this uses AF_UNIX sockets.
+On Windows, this uses NamedPipes.
+"""
+
+from __future__ import annotations
+
+import json
+import os
+import shutil
+import struct
+import sys
+import tempfile
+from abc import abstractmethod
+from collections.abc import Callable
+from select import select
+from types import TracebackType
+from typing import Final
+from typing_extensions import Self
+
+from librt.base64 import urlsafe_b64encode
+from librt.internal import ReadBuffer, WriteBuffer
+
+if sys.platform == "win32":
+    # This may be private, but it is needed for IPC on Windows, and is basically stable
+    import _winapi
+    import ctypes
+
+    _IPCHandle = int
+
+    kernel32 = ctypes.windll.kernel32
+    DisconnectNamedPipe: Callable[[_IPCHandle], int] = kernel32.DisconnectNamedPipe
+    FlushFileBuffers: Callable[[_IPCHandle], int] = kernel32.FlushFileBuffers
+else:
+    import socket
+
+    _IPCHandle = socket.socket
+
+# Size of the message packed as !L, i.e. 4 bytes in network order (big-endian).
+HEADER_SIZE = 4
+
+
+# TODO: we should make sure consistent exceptions are raised on different platforms.
+# Currently we raise either IPCException or OSError for equivalent conditions.
+class IPCException(Exception):
+    """Exception for IPC issues."""
+
+
+class IPCBase:
+    """Base class for communication between the dmypy client and server.
+
+    This contains logic shared between the client and server, such as reading
+    and writing.
+    We want to be able to send multiple "messages" over a single connection and
+    to be able to separate the messages. We do this by prefixing each message
+    with its size in a fixed format.
+    """
+
+    connection: _IPCHandle
+
+    def __init__(self, name: str, timeout: float | None) -> None:
+        self.name = name
+        self.timeout = timeout
+        self.message_size: int | None = None
+        self.buffer = bytearray()
+
+    def frame_from_buffer(self) -> bytes | None:
+        """Return a full frame from the bytes we have in the buffer."""
+        size = len(self.buffer)
+        if size < HEADER_SIZE:
+            return None
+        if self.message_size is None:
+            self.message_size = struct.unpack("!L", self.buffer[:HEADER_SIZE])[0]
+        if size < self.message_size + HEADER_SIZE:
+            return None
+        # We have a full frame, avoid extra copy in case we get a large frame.
+        bdata = memoryview(self.buffer)[HEADER_SIZE : HEADER_SIZE + self.message_size]
+        self.buffer = self.buffer[HEADER_SIZE + self.message_size :]
+        self.message_size = None
+        return bytes(bdata)
+
+    def read(self, size: int = 100000) -> str:
+        return self.read_bytes(size).decode("utf-8")
+
+    def read_bytes(self, size: int = 100000) -> bytes:
+        """Read bytes from an IPC connection until we have a full frame."""
+        if sys.platform == "win32":
+            while True:
+                # Check if we already have a message in the buffer before
+                # receiving any more data from the socket.
+                bdata = self.frame_from_buffer()
+                if bdata is not None:
+                    break
+
+                # Receive more data into the buffer.
+                ov, err = _winapi.ReadFile(self.connection, size, overlapped=True)
+                try:
+                    if err == _winapi.ERROR_IO_PENDING:
+                        timeout = int(self.timeout * 1000) if self.timeout else _winapi.INFINITE
+                        res = _winapi.WaitForSingleObject(ov.event, timeout)
+                        if res != _winapi.WAIT_OBJECT_0:
+                            raise IPCException(f"Bad result from I/O wait: {res}")
+                except BaseException:
+                    ov.cancel()
+                    raise
+                _, err = ov.GetOverlappedResult(True)
+                more = ov.getbuffer()
+                if more:
+                    self.buffer.extend(more)
+                    bdata = self.frame_from_buffer()
+                    if bdata is not None:
+                        break
+                if err == 0:
+                    # we are done!
+                    break
+                elif err == _winapi.ERROR_MORE_DATA:
+                    # read again
+                    continue
+                elif err == _winapi.ERROR_OPERATION_ABORTED:
+                    raise IPCException("ReadFile operation aborted.")
+        else:
+            while True:
+                # Check if we already have a message in the buffer before
+                # receiving any more data from the socket.
+                bdata = self.frame_from_buffer()
+                if bdata is not None:
+                    break
+
+                # Receive more data into the buffer.
+                more = self.connection.recv(size)
+                if not more:
+                    # Connection closed
+                    break
+                self.buffer.extend(more)
+
+        if not bdata:
+            # Socket was empty, and we didn't get any frame.
+            # This should only happen if the socket was closed.
+            return b""
+        return bdata
+
+    def write(self, data: str) -> None:
+        self.write_bytes(data.encode("utf-8"))
+
+    def write_bytes(self, data: bytes) -> None:
+        """Write to an IPC connection."""
+
+        # Frame the data by adding fixed size header.
+        encoded_data = struct.pack("!L", len(data)) + data
+
+        if sys.platform == "win32":
+            try:
+                ov, err = _winapi.WriteFile(self.connection, encoded_data, overlapped=True)
+                try:
+                    if err == _winapi.ERROR_IO_PENDING:
+                        timeout = int(self.timeout * 1000) if self.timeout else _winapi.INFINITE
+                        res = _winapi.WaitForSingleObject(ov.event, timeout)
+                        if res != _winapi.WAIT_OBJECT_0:
+                            raise IPCException(f"Bad result from I/O wait: {res}")
+                    elif err != 0:
+                        raise IPCException(f"Failed writing to pipe with error: {err}")
+                except BaseException:
+                    ov.cancel()
+                    raise
+                bytes_written, err = ov.GetOverlappedResult(True)
+                assert err == 0, err
+                assert bytes_written == len(encoded_data)
+            except OSError as e:
+                raise IPCException(f"Failed to write with error: {e.winerror}") from e
+        else:
+            self.connection.sendall(encoded_data)
+
+    def close(self) -> None:
+        if sys.platform == "win32":
+            if self.connection != _winapi.NULL:
+                _winapi.CloseHandle(self.connection)
+        else:
+            self.connection.close()
+
+
+class IPCClient(IPCBase):
+    """The client side of an IPC connection."""
+
+    def __init__(self, name: str, timeout: float | None) -> None:
+        super().__init__(name, timeout)
+        if sys.platform == "win32":
+            timeout = int(self.timeout * 1000) if self.timeout else _winapi.NMPWAIT_WAIT_FOREVER
+            try:
+                _winapi.WaitNamedPipe(self.name, timeout)
+            except FileNotFoundError as e:
+                raise IPCException(f"The NamedPipe at {self.name} was not found.") from e
+            except OSError as e:
+                if e.winerror == _winapi.ERROR_SEM_TIMEOUT:
+                    raise IPCException("Timed out waiting for connection.") from e
+                else:
+                    raise
+            try:
+                self.connection = _winapi.CreateFile(
+                    self.name,
+                    _winapi.GENERIC_READ | _winapi.GENERIC_WRITE,
+                    0,
+                    _winapi.NULL,
+                    _winapi.OPEN_EXISTING,
+                    _winapi.FILE_FLAG_OVERLAPPED,
+                    _winapi.NULL,
+                )
+            except OSError as e:
+                if e.winerror == _winapi.ERROR_PIPE_BUSY:
+                    raise IPCException("The connection is busy.") from e
+                else:
+                    raise
+            _winapi.SetNamedPipeHandleState(
+                self.connection, _winapi.PIPE_READMODE_MESSAGE, None, None
+            )
+        else:
+            self.connection = socket.socket(socket.AF_UNIX)
+            self.connection.settimeout(timeout)
+            self.connection.connect(name)
+
+    def __enter__(self) -> IPCClient:
+        return self
+
+    def __exit__(
+        self,
+        exc_ty: type[BaseException] | None = None,
+        exc_val: BaseException | None = None,
+        exc_tb: TracebackType | None = None,
+    ) -> None:
+        self.close()
+
+
+class IPCServer(IPCBase):
+    BUFFER_SIZE: Final = 2**16
+
+    def __init__(self, name: str, timeout: float | None = None) -> None:
+        if sys.platform == "win32":
+            name = r"\\.\pipe\{}-{}.pipe".format(name, urlsafe_b64encode(os.urandom(6)).decode())
+        else:
+            name = f"{name}.sock"
+        super().__init__(name, timeout)
+        if sys.platform == "win32":
+            self.connection = _winapi.CreateNamedPipe(
+                self.name,
+                _winapi.PIPE_ACCESS_DUPLEX
+                | _winapi.FILE_FLAG_FIRST_PIPE_INSTANCE
+                | _winapi.FILE_FLAG_OVERLAPPED,
+                _winapi.PIPE_READMODE_MESSAGE
+                | _winapi.PIPE_TYPE_MESSAGE
+                | _winapi.PIPE_WAIT
+                | 0x8,  # PIPE_REJECT_REMOTE_CLIENTS
+                1,  # one instance
+                self.BUFFER_SIZE,
+                self.BUFFER_SIZE,
+                _winapi.NMPWAIT_WAIT_FOREVER,
+                0,  # Use default security descriptor
+            )
+            if self.connection == -1:  # INVALID_HANDLE_VALUE
+                err = _winapi.GetLastError()
+                raise IPCException(f"Invalid handle to pipe: {err}")
+        else:
+            self.sock_directory = tempfile.mkdtemp()
+            sockfile = os.path.join(self.sock_directory, self.name)
+            self.sock = socket.socket(socket.AF_UNIX)
+            self.sock.bind(sockfile)
+            self.sock.listen(1)
+            if timeout is not None:
+                self.sock.settimeout(timeout)
+
+    def __enter__(self) -> IPCServer:
+        if sys.platform == "win32":
+            # NOTE: It is theoretically possible that this will hang forever if the
+            # client never connects, though this can be "solved" by killing the server
+            try:
+                ov = _winapi.ConnectNamedPipe(self.connection, overlapped=True)
+            except OSError as e:
+                # Don't raise if the client already exists, or the client already connected
+                if e.winerror not in (_winapi.ERROR_PIPE_CONNECTED, _winapi.ERROR_NO_DATA):
+                    raise
+            else:
+                try:
+                    timeout = int(self.timeout * 1000) if self.timeout else _winapi.INFINITE
+                    res = _winapi.WaitForSingleObject(ov.event, timeout)
+                    assert res == _winapi.WAIT_OBJECT_0
+                except BaseException:
+                    ov.cancel()
+                    _winapi.CloseHandle(self.connection)
+                    raise
+                _, err = ov.GetOverlappedResult(True)
+                assert err == 0
+        else:
+            try:
+                self.connection, _ = self.sock.accept()
+            except TimeoutError as e:
+                raise IPCException("The socket timed out") from e
+        return self
+
+    def __exit__(
+        self,
+        exc_ty: type[BaseException] | None = None,
+        exc_val: BaseException | None = None,
+        exc_tb: TracebackType | None = None,
+    ) -> None:
+        if sys.platform == "win32":
+            try:
+                # Wait for the client to finish reading the last write before disconnecting
+                if not FlushFileBuffers(self.connection):
+                    raise IPCException(
+                        "Failed to flush NamedPipe buffer, maybe the client hung up?"
+                    )
+            finally:
+                DisconnectNamedPipe(self.connection)
+        else:
+            self.close()
+
+    def cleanup(self) -> None:
+        if sys.platform == "win32":
+            self.close()
+        else:
+            shutil.rmtree(self.sock_directory)
+
+    @property
+    def connection_name(self) -> str:
+        if sys.platform == "win32":
+            return self.name
+        elif sys.platform == "gnu0":
+            # GNU/Hurd returns empty string from getsockname()
+            # for AF_UNIX sockets
+            return os.path.join(self.sock_directory, self.name)
+        else:
+            name = self.sock.getsockname()
+            assert isinstance(name, str)
+            return name
+
+
+class BadStatus(Exception):
+    """Exception raised when there is something wrong with the status file.
+
+    For example:
+    - No status file found
+    - Status file malformed
+    - Process whose pid is in the status file does not exist
+    """
+
+
+def read_status(status_file: str) -> dict[str, object]:
+    """Read status file.
+
+    Raise BadStatus if the status file doesn't exist or contains
+    invalid JSON or the JSON is not a dict.
+    """
+    if not os.path.isfile(status_file):
+        raise BadStatus("No status file found")
+    with open(status_file) as f:
+        try:
+            data = json.load(f)
+        except Exception as e:
+            raise BadStatus(f"Malformed status file: {str(e)}") from e
+    if not isinstance(data, dict):
+        raise BadStatus(f"Invalid status file (not a dict): {data}")
+    return data
+
+
+def ready_to_read(conns: list[IPCClient], timeout: float | None = None) -> list[int]:
+    """Wait until some connections are readable.
+
+    Return index of each readable connection in the original list.
+    """
+    if sys.platform == "win32":
+        # Windows doesn't support select() on named pipes. Instead, start an overlapped
+        # ReadFile on each pipe (which internally creates an event via CreateEventW),
+        # then WaitForMultipleObjects on those events for efficient OS-level waiting.
+        # Any data consumed by the probe reads is stored into each connection's buffer
+        # so the subsequent read_bytes() call will find it via frame_from_buffer().
+        WAIT_FAILED = 0xFFFFFFFF
+        pending: list[tuple[int, _winapi.Overlapped]] = []
+        events: list[int] = []
+        ready: list[int] = []
+
+        for i, conn in enumerate(conns):
+            try:
+                ov, err = _winapi.ReadFile(conn.connection, 1, overlapped=True)
+            except OSError:
+                # Broken/closed pipe. Mimic Linux behavior here, caller will get
+                # the exception when trying to read from this socket.
+                ready.append(i)
+                continue
+            if err == _winapi.ERROR_IO_PENDING:
+                events.append(ov.event)
+                pending.append((i, ov))
+            else:
+                # Data was immediately available (err == 0 or ERROR_MORE_DATA)
+                _, err = ov.GetOverlappedResult(True)
+                data = ov.getbuffer()
+                if data:
+                    conn.buffer.extend(data)
+                ready.append(i)
+
+        # Wait only if nothing is immediately ready and there are pending operations
+        if not ready and events:
+            timeout_ms = int(timeout * 1000) if timeout is not None else _winapi.INFINITE
+            res = _winapi.WaitForMultipleObjects(events, False, timeout_ms)
+            if res == WAIT_FAILED:
+                for _, ov in pending:
+                    ov.cancel()
+                raise IPCException(f"Failed to wait for connections: {_winapi.GetLastError()}")
+
+        # Check which pending operations completed, cancel the rest
+        for i, ov in pending:
+            if _winapi.WaitForSingleObject(ov.event, 0) == _winapi.WAIT_OBJECT_0:
+                _, err = ov.GetOverlappedResult(True)
+                data = ov.getbuffer()
+                if data:
+                    conns[i].buffer.extend(data)
+                ready.append(i)
+            else:
+                ov.cancel()
+
+        return ready
+
+    else:
+        connections = [conn.connection for conn in conns]
+        ready, _, _ = select(connections, [], [], timeout)
+        return [connections.index(r) for r in ready]
+
+
+def send(connection: IPCBase, data: IPCMessage) -> None:
+    """Send data to a connection encoded and framed.
+
+    The data must be a non-abstract IPCMessage. We assume that a single send call is a
+    single frame to be sent.
+    """
+    buf = WriteBuffer()
+    data.write(buf)
+    connection.write_bytes(buf.getvalue())
+
+
+def receive(connection: IPCBase) -> ReadBuffer:
+    """Receive single encoded IPCMessage frame from a connection.
+
+    Raise OSError if the data received is not valid.
+    """
+    bdata = connection.read_bytes()
+    if not bdata:
+        raise OSError("No data received")
+    return ReadBuffer(bdata)
+
+
+class IPCMessage:
+    @classmethod
+    @abstractmethod
+    def read(cls, buf: ReadBuffer) -> Self:
+        raise NotImplementedError
+
+    @abstractmethod
+    def write(self, buf: WriteBuffer) -> None:
+        raise NotImplementedError

venv/lib/python3.11/site-packages/mypy/join.py

@@ -0,0 +1,916 @@
+"""Calculation of the least upper bound types (joins)."""
+
+from __future__ import annotations
+
+from collections.abc import Sequence
+from typing import overload
+
+import mypy.typeops
+from mypy.expandtype import expand_type
+from mypy.maptype import map_instance_to_supertype
+from mypy.nodes import CONTRAVARIANT, COVARIANT, INVARIANT, VARIANCE_NOT_READY, TypeInfo
+from mypy.state import state
+from mypy.subtypes import (
+    SubtypeContext,
+    find_member,
+    is_equivalent,
+    is_proper_subtype,
+    is_protocol_implementation,
+    is_subtype,
+)
+from mypy.types import (
+    AnyType,
+    CallableType,
+    DeletedType,
+    ErasedType,
+    FunctionLike,
+    Instance,
+    LiteralType,
+    NoneType,
+    Overloaded,
+    Parameters,
+    ParamSpecType,
+    PartialType,
+    ProperType,
+    TupleType,
+    Type,
+    TypeAliasType,
+    TypedDictType,
+    TypeOfAny,
+    TypeType,
+    TypeVarId,
+    TypeVarLikeType,
+    TypeVarTupleType,
+    TypeVarType,
+    TypeVisitor,
+    UnboundType,
+    UninhabitedType,
+    UnionType,
+    UnpackType,
+    find_unpack_in_list,
+    get_proper_type,
+    get_proper_types,
+    split_with_prefix_and_suffix,
+)
+
+
+class InstanceJoiner:
+    def __init__(self) -> None:
+        self.seen_instances: list[tuple[Instance, Instance]] = []
+
+    def join_instances(self, t: Instance, s: Instance) -> ProperType:
+        if (t, s) in self.seen_instances or (s, t) in self.seen_instances:
+            return object_from_instance(t)
+
+        self.seen_instances.append((t, s))
+
+        # Calculate the join of two instance types
+        if t.type == s.type:
+            # Simplest case: join two types with the same base type (but
+            # potentially different arguments).
+
+            # Combine type arguments.
+            args: list[Type] = []
+            # N.B: We use zip instead of indexing because the lengths might have
+            # mismatches during daemon reprocessing.
+            if t.type.has_type_var_tuple_type:
+                # We handle joins of variadic instances by simply creating correct mapping
+                # for type arguments and compute the individual joins same as for regular
+                # instances. All the heavy lifting is done in the join of tuple types.
+                assert s.type.type_var_tuple_prefix is not None
+                assert s.type.type_var_tuple_suffix is not None
+                prefix = s.type.type_var_tuple_prefix
+                suffix = s.type.type_var_tuple_suffix
+                tvt = s.type.defn.type_vars[prefix]
+                assert isinstance(tvt, TypeVarTupleType)
+                fallback = tvt.tuple_fallback
+                s_prefix, s_middle, s_suffix = split_with_prefix_and_suffix(s.args, prefix, suffix)
+                t_prefix, t_middle, t_suffix = split_with_prefix_and_suffix(t.args, prefix, suffix)
+                s_args = s_prefix + (TupleType(list(s_middle), fallback),) + s_suffix
+                t_args = t_prefix + (TupleType(list(t_middle), fallback),) + t_suffix
+            else:
+                t_args = t.args
+                s_args = s.args
+            for ta, sa, type_var in zip(t_args, s_args, t.type.defn.type_vars):
+                ta_proper = get_proper_type(ta)
+                sa_proper = get_proper_type(sa)
+                new_type: Type | None = None
+                if isinstance(ta_proper, AnyType):
+                    new_type = AnyType(TypeOfAny.from_another_any, ta_proper)
+                elif isinstance(sa_proper, AnyType):
+                    new_type = AnyType(TypeOfAny.from_another_any, sa_proper)
+                elif isinstance(type_var, TypeVarType):
+                    if type_var.variance in (COVARIANT, VARIANCE_NOT_READY):
+                        new_type = join_types(ta, sa, self)
+                        if len(type_var.values) != 0 and new_type not in type_var.values:
+                            self.seen_instances.pop()
+                            return object_from_instance(t)
+                        if not is_subtype(new_type, type_var.upper_bound):
+                            self.seen_instances.pop()
+                            return object_from_instance(t)
+                    # TODO: contravariant case should use meet but pass seen instances as
+                    # an argument to keep track of recursive checks.
+                    elif type_var.variance in (INVARIANT, CONTRAVARIANT):
+                        if isinstance(ta_proper, UninhabitedType) and ta_proper.ambiguous:
+                            new_type = sa
+                        elif isinstance(sa_proper, UninhabitedType) and sa_proper.ambiguous:
+                            new_type = ta
+                        elif not is_equivalent(ta, sa):
+                            self.seen_instances.pop()
+                            return object_from_instance(t)
+                        else:
+                            # If the types are different but equivalent, then an Any is involved
+                            # so using a join in the contravariant case is also OK.
+                            new_type = join_types(ta, sa, self)
+                elif isinstance(type_var, TypeVarTupleType):
+                    new_type = get_proper_type(join_types(ta, sa, self))
+                    # Put the joined arguments back into instance in the normal form:
+                    #   a) Tuple[X, Y, Z] -> [X, Y, Z]
+                    #   b) tuple[X, ...] -> [*tuple[X, ...]]
+                    if isinstance(new_type, Instance):
+                        assert new_type.type.fullname == "builtins.tuple"
+                        new_type = UnpackType(new_type)
+                    else:
+                        assert isinstance(new_type, TupleType)
+                        args.extend(new_type.items)
+                        continue
+                else:
+                    # ParamSpec type variables behave the same, independent of variance
+                    if not is_equivalent(ta, sa):
+                        return get_proper_type(type_var.upper_bound)
+                    new_type = join_types(ta, sa, self)
+                assert new_type is not None
+                args.append(new_type)
+            result: ProperType = Instance(t.type, args)
+        elif t.type.bases and is_proper_subtype(
+            t, s, subtype_context=SubtypeContext(ignore_type_params=True)
+        ):
+            result = self.join_instances_via_supertype(t, s)
+        else:
+            # Now t is not a subtype of s, and t != s. Now s could be a subtype
+            # of t; alternatively, we need to find a common supertype. This works
+            # in of the both cases.
+            result = self.join_instances_via_supertype(s, t)
+
+        self.seen_instances.pop()
+        return result
+
+    def join_instances_via_supertype(self, t: Instance, s: Instance) -> ProperType:
+        # Give preference to joins via duck typing relationship, so that
+        # join(int, float) == float, for example.
+        for p in t.type._promote:
+            if is_subtype(p, s):
+                return join_types(p, s, self)
+        for p in s.type._promote:
+            if is_subtype(p, t):
+                return join_types(t, p, self)
+
+        # Compute the "best" supertype of t when joined with s.
+        # The definition of "best" may evolve; for now it is the one with
+        # the longest MRO.  Ties are broken by using the earlier base.
+
+        # Go over both sets of bases in case there's an explicit Protocol base. This is important
+        # to ensure commutativity of join (although in cases where both classes have relevant
+        # Protocol bases this maybe might still not be commutative)
+        base_types: dict[TypeInfo, None] = {}  # dict to deduplicate but preserve order
+        for base in t.type.bases:
+            base_types[base.type] = None
+        for base in s.type.bases:
+            if base.type.is_protocol and is_subtype(t, base):
+                base_types[base.type] = None
+
+        best: ProperType | None = None
+        for base_type in base_types:
+            mapped = map_instance_to_supertype(t, base_type)
+            res = self.join_instances(mapped, s)
+            if best is None or is_better(res, best):
+                best = res
+        assert best is not None
+        for promote in t.type._promote:
+            if isinstance(promote, Instance):
+                res = self.join_instances(promote, s)
+                if is_better(res, best):
+                    best = res
+        return best
+
+
+def trivial_join(s: Type, t: Type) -> Type:
+    """Return one of types (expanded) if it is a supertype of other, otherwise top type."""
+    if is_subtype(s, t):
+        return t
+    elif is_subtype(t, s):
+        return s
+    else:
+        return object_or_any_from_type(get_proper_type(t))
+
+
+@overload
+def join_types(
+    s: ProperType, t: ProperType, instance_joiner: InstanceJoiner | None = None
+) -> ProperType: ...
+
+
+@overload
+def join_types(s: Type, t: Type, instance_joiner: InstanceJoiner | None = None) -> Type: ...
+
+
+def join_types(s: Type, t: Type, instance_joiner: InstanceJoiner | None = None) -> Type:
+    """Return the least upper bound of s and t.
+
+    For example, the join of 'int' and 'object' is 'object'.
+    """
+    if mypy.typeops.is_recursive_pair(s, t):
+        # This case can trigger an infinite recursion, general support for this will be
+        # tricky so we use a trivial join (like for protocols).
+        return trivial_join(s, t)
+    s = get_proper_type(s)
+    t = get_proper_type(t)
+
+    if (s.can_be_true, s.can_be_false) != (t.can_be_true, t.can_be_false):
+        # if types are restricted in different ways, use the more general versions
+        s = mypy.typeops.true_or_false(s)
+        t = mypy.typeops.true_or_false(t)
+
+    if isinstance(s, UnionType) and not isinstance(t, UnionType):
+        s, t = t, s
+
+    if isinstance(s, AnyType):
+        return s
+
+    if isinstance(s, ErasedType):
+        return t
+
+    if isinstance(s, NoneType) and not isinstance(t, NoneType):
+        s, t = t, s
+
+    if isinstance(s, UninhabitedType) and not isinstance(t, UninhabitedType):
+        s, t = t, s
+
+    # Meets/joins require callable type normalization.
+    s, t = normalize_callables(s, t)
+
+    # Use a visitor to handle non-trivial cases.
+    return t.accept(TypeJoinVisitor(s, instance_joiner))
+
+
+class TypeJoinVisitor(TypeVisitor[ProperType]):
+    """Implementation of the least upper bound algorithm.
+
+    Attributes:
+      s: The other (left) type operand.
+    """
+
+    def __init__(self, s: ProperType, instance_joiner: InstanceJoiner | None = None) -> None:
+        self.s = s
+        self.instance_joiner = instance_joiner
+
+    def visit_unbound_type(self, t: UnboundType) -> ProperType:
+        return AnyType(TypeOfAny.special_form)
+
+    def visit_union_type(self, t: UnionType) -> ProperType:
+        if is_proper_subtype(self.s, t):
+            return t
+        else:
+            return mypy.typeops.make_simplified_union([self.s, t])
+
+    def visit_any(self, t: AnyType) -> ProperType:
+        return t
+
+    def visit_none_type(self, t: NoneType) -> ProperType:
+        if state.strict_optional:
+            if isinstance(self.s, (NoneType, UninhabitedType)):
+                return t
+            elif isinstance(self.s, (UnboundType, AnyType)):
+                return AnyType(TypeOfAny.special_form)
+            else:
+                return mypy.typeops.make_simplified_union([self.s, t])
+        else:
+            return self.s
+
+    def visit_uninhabited_type(self, t: UninhabitedType) -> ProperType:
+        return self.s
+
+    def visit_deleted_type(self, t: DeletedType) -> ProperType:
+        return self.s
+
+    def visit_erased_type(self, t: ErasedType) -> ProperType:
+        return self.s
+
+    def visit_type_var(self, t: TypeVarType) -> ProperType:
+        if isinstance(self.s, TypeVarType):
+            if self.s.id == t.id:
+                if self.s.upper_bound == t.upper_bound:
+                    return self.s
+                return self.s.copy_modified(
+                    upper_bound=join_types(self.s.upper_bound, t.upper_bound)
+                )
+            # Fix non-commutative joins
+            return get_proper_type(join_types(self.s.upper_bound, t.upper_bound))
+        else:
+            return self.default(self.s)
+
+    def visit_param_spec(self, t: ParamSpecType) -> ProperType:
+        if self.s == t:
+            return t
+        return self.default(self.s)
+
+    def visit_type_var_tuple(self, t: TypeVarTupleType) -> ProperType:
+        if self.s == t:
+            return t
+        if isinstance(self.s, Instance) and is_subtype(t.upper_bound, self.s):
+            # TODO: should we do this more generally and for all TypeVarLikeTypes?
+            return self.s
+        return self.default(self.s)
+
+    def visit_unpack_type(self, t: UnpackType) -> UnpackType:
+        raise NotImplementedError
+
+    def visit_parameters(self, t: Parameters) -> ProperType:
+        if isinstance(self.s, Parameters):
+            if not is_similar_params(t, self.s):
+                # TODO: it would be prudent to return [*object, **object] instead of Any.
+                return self.default(self.s)
+            from mypy.meet import meet_types
+
+            return t.copy_modified(
+                arg_types=[
+                    meet_types(s_a, t_a) for s_a, t_a in zip(self.s.arg_types, t.arg_types)
+                ],
+                arg_names=combine_arg_names(self.s, t),
+            )
+        else:
+            return self.default(self.s)
+
+    def visit_instance(self, t: Instance) -> ProperType:
+        if isinstance(self.s, Instance):
+            if self.instance_joiner is None:
+                self.instance_joiner = InstanceJoiner()
+            nominal = self.instance_joiner.join_instances(t, self.s)
+            structural: Instance | None = None
+            if t.type.is_protocol and is_protocol_implementation(self.s, t):
+                structural = t
+            elif self.s.type.is_protocol and is_protocol_implementation(t, self.s):
+                structural = self.s
+            # Structural join is preferred in the case where we have found both
+            # structural and nominal and they have same MRO length (see two comments
+            # in join_instances_via_supertype). Otherwise, just return the nominal join.
+            if not structural or is_better(nominal, structural):
+                return nominal
+            return structural
+        elif isinstance(self.s, FunctionLike):
+            if t.type.is_protocol:
+                call = unpack_callback_protocol(t)
+                if call:
+                    return join_types(call, self.s)
+            return join_types(t, self.s.fallback)
+        elif isinstance(self.s, TypeType):
+            return join_types(t, self.s)
+        elif isinstance(self.s, TypedDictType):
+            return join_types(t, self.s)
+        elif isinstance(self.s, TupleType):
+            return join_types(t, self.s)
+        elif isinstance(self.s, LiteralType):
+            return join_types(t, self.s)
+        elif isinstance(self.s, TypeVarTupleType) and is_subtype(self.s.upper_bound, t):
+            return t
+        else:
+            return self.default(self.s)
+
+    def visit_callable_type(self, t: CallableType) -> ProperType:
+        if isinstance(self.s, CallableType):
+            if is_similar_callables(t, self.s):
+                if is_equivalent(t, self.s):
+                    return combine_similar_callables(t, self.s)
+                result = join_similar_callables(t, self.s)
+                if any(
+                    isinstance(tp, (NoneType, UninhabitedType))
+                    for tp in get_proper_types(result.arg_types)
+                ):
+                    # We don't want to return unusable Callable, attempt fallback instead.
+                    return join_types(t.fallback, self.s)
+                # We set the from_type_type flag to suppress error when a collection of
+                # concrete class objects gets inferred as their common abstract superclass.
+                if not (
+                    (t.is_type_obj() and t.type_object().is_abstract)
+                    or (self.s.is_type_obj() and self.s.type_object().is_abstract)
+                ):
+                    result.from_type_type = True
+                return result
+            else:
+                s2, t2 = self.s, t
+                if t2.is_var_arg:
+                    s2, t2 = t2, s2
+                if is_subtype(s2, t2):
+                    return t2.copy_modified()
+                elif is_subtype(t2, s2):
+                    return s2.copy_modified()
+                return join_types(t.fallback, self.s)
+        elif isinstance(self.s, Overloaded):
+            # Switch the order of arguments to that we'll get to visit_overloaded.
+            return join_types(t, self.s)
+        elif isinstance(self.s, Instance) and self.s.type.is_protocol:
+            call = unpack_callback_protocol(self.s)
+            if call:
+                return join_types(t, call)
+        return join_types(t.fallback, self.s)
+
+    def visit_overloaded(self, t: Overloaded) -> ProperType:
+        # This is more complex than most other cases. Here are some
+        # examples that illustrate how this works.
+        #
+        # First let's define a concise notation:
+        #  - Cn are callable types (for n in 1, 2, ...)
+        #  - Ov(C1, C2, ...) is an overloaded type with items C1, C2, ...
+        #  - Callable[[T, ...], S] is written as [T, ...] -> S.
+        #
+        # We want some basic properties to hold (assume Cn are all
+        # unrelated via Any-similarity):
+        #
+        #   join(Ov(C1, C2), C1) == C1
+        #   join(Ov(C1, C2), Ov(C1, C2)) == Ov(C1, C2)
+        #   join(Ov(C1, C2), Ov(C1, C3)) == C1
+        #   join(Ov(C2, C2), C3) == join of fallback types
+        #
+        # The presence of Any types makes things more interesting. The join is the
+        # most general type we can get with respect to Any:
+        #
+        #   join(Ov([int] -> int, [str] -> str), [Any] -> str) == Any -> str
+        #
+        # We could use a simplification step that removes redundancies, but that's not
+        # implemented right now. Consider this example, where we get a redundancy:
+        #
+        #   join(Ov([int, Any] -> Any, [str, Any] -> Any), [Any, int] -> Any) ==
+        #       Ov([Any, int] -> Any, [Any, int] -> Any)
+        #
+        # TODO: Consider more cases of callable subtyping.
+        result: list[CallableType] = []
+        s = self.s
+        if isinstance(s, FunctionLike):
+            # The interesting case where both types are function types.
+            for t_item in t.items:
+                for s_item in s.items:
+                    if is_similar_callables(t_item, s_item):
+                        if is_equivalent(t_item, s_item):
+                            result.append(combine_similar_callables(t_item, s_item))
+                        elif is_subtype(t_item, s_item):
+                            result.append(s_item)
+            if result:
+                # TODO: Simplify redundancies from the result.
+                if len(result) == 1:
+                    return result[0]
+                else:
+                    return Overloaded(result)
+            return join_types(t.fallback, s.fallback)
+        elif isinstance(s, Instance) and s.type.is_protocol:
+            call = unpack_callback_protocol(s)
+            if call:
+                return join_types(t, call)
+        return join_types(t.fallback, s)
+
+    def join_tuples(self, s: TupleType, t: TupleType) -> list[Type] | None:
+        """Join two tuple types while handling variadic entries.
+
+        This is surprisingly tricky, and we don't handle some tricky corner cases.
+        Most of the trickiness comes from the variadic tuple items like *tuple[X, ...]
+        since they can have arbitrary partial overlaps (while *Ts can't be split).
+        """
+        s_unpack_index = find_unpack_in_list(s.items)
+        t_unpack_index = find_unpack_in_list(t.items)
+        if s_unpack_index is None and t_unpack_index is None:
+            if s.length() == t.length():
+                items: list[Type] = []
+                for i in range(t.length()):
+                    items.append(join_types(t.items[i], s.items[i]))
+                return items
+            return None
+        if s_unpack_index is not None and t_unpack_index is not None:
+            # The most complex case: both tuples have an unpack item.
+            s_unpack = s.items[s_unpack_index]
+            assert isinstance(s_unpack, UnpackType)
+            s_unpacked = get_proper_type(s_unpack.type)
+            t_unpack = t.items[t_unpack_index]
+            assert isinstance(t_unpack, UnpackType)
+            t_unpacked = get_proper_type(t_unpack.type)
+            if s.length() == t.length() and s_unpack_index == t_unpack_index:
+                # We can handle a case where arity is perfectly aligned, e.g.
+                # join(Tuple[X1, *tuple[Y1, ...], Z1], Tuple[X2, *tuple[Y2, ...], Z2]).
+                # We can essentially perform the join elementwise.
+                prefix_len = t_unpack_index
+                suffix_len = t.length() - t_unpack_index - 1
+                items = []
+                for si, ti in zip(s.items[:prefix_len], t.items[:prefix_len]):
+                    items.append(join_types(si, ti))
+                joined = join_types(s_unpacked, t_unpacked)
+                if isinstance(joined, TypeVarTupleType):
+                    items.append(UnpackType(joined))
+                elif isinstance(joined, Instance) and joined.type.fullname == "builtins.tuple":
+                    items.append(UnpackType(joined))
+                else:
+                    if isinstance(t_unpacked, Instance):
+                        assert t_unpacked.type.fullname == "builtins.tuple"
+                        tuple_instance = t_unpacked
+                    else:
+                        assert isinstance(t_unpacked, TypeVarTupleType)
+                        tuple_instance = t_unpacked.tuple_fallback
+                    items.append(
+                        UnpackType(
+                            tuple_instance.copy_modified(
+                                args=[object_from_instance(tuple_instance)]
+                            )
+                        )
+                    )
+                if suffix_len:
+                    for si, ti in zip(s.items[-suffix_len:], t.items[-suffix_len:]):
+                        items.append(join_types(si, ti))
+                return items
+            if s.length() == 1 or t.length() == 1:
+                # Another case we can handle is when one of tuple is purely variadic
+                # (i.e. a non-normalized form of tuple[X, ...]), in this case the join
+                # will be again purely variadic.
+                if not (isinstance(s_unpacked, Instance) and isinstance(t_unpacked, Instance)):
+                    return None
+                assert s_unpacked.type.fullname == "builtins.tuple"
+                assert t_unpacked.type.fullname == "builtins.tuple"
+                mid_joined = join_types(s_unpacked.args[0], t_unpacked.args[0])
+                t_other = [a for i, a in enumerate(t.items) if i != t_unpack_index]
+                s_other = [a for i, a in enumerate(s.items) if i != s_unpack_index]
+                other_joined = join_type_list(s_other + t_other)
+                mid_joined = join_types(mid_joined, other_joined)
+                return [UnpackType(s_unpacked.copy_modified(args=[mid_joined]))]
+            # TODO: are there other case we can handle (e.g. both prefix/suffix are shorter)?
+            return None
+        if s_unpack_index is not None:
+            variadic = s
+            unpack_index = s_unpack_index
+            fixed = t
+        else:
+            assert t_unpack_index is not None
+            variadic = t
+            unpack_index = t_unpack_index
+            fixed = s
+        # Case where one tuple has variadic item and the other one doesn't. The join will
+        # be variadic, since fixed tuple is a subtype of variadic, but not vice versa.
+        unpack = variadic.items[unpack_index]
+        assert isinstance(unpack, UnpackType)
+        unpacked = get_proper_type(unpack.type)
+        if not isinstance(unpacked, Instance):
+            return None
+        if fixed.length() < variadic.length() - 1:
+            # There are no non-trivial types that are supertype of both.
+            return None
+        prefix_len = unpack_index
+        suffix_len = variadic.length() - prefix_len - 1
+        prefix, middle, suffix = split_with_prefix_and_suffix(
+            tuple(fixed.items), prefix_len, suffix_len
+        )
+        items = []
+        for fi, vi in zip(prefix, variadic.items[:prefix_len]):
+            items.append(join_types(fi, vi))
+        mid_joined = join_type_list(list(middle))
+        mid_joined = join_types(mid_joined, unpacked.args[0])
+        items.append(UnpackType(unpacked.copy_modified(args=[mid_joined])))
+        if suffix_len:
+            for fi, vi in zip(suffix, variadic.items[-suffix_len:]):
+                items.append(join_types(fi, vi))
+        return items
+
+    def visit_tuple_type(self, t: TupleType) -> ProperType:
+        # When given two fixed-length tuples:
+        # * If they have the same length, join their subtypes item-wise:
+        #   Tuple[int, bool] + Tuple[bool, bool] becomes Tuple[int, bool]
+        # * If lengths do not match, return a variadic tuple:
+        #   Tuple[bool, int] + Tuple[bool] becomes Tuple[int, ...]
+        #
+        # Otherwise, `t` is a fixed-length tuple but `self.s` is NOT:
+        # * Joining with a variadic tuple returns variadic tuple:
+        #   Tuple[int, bool] + Tuple[bool, ...] becomes Tuple[int, ...]
+        # * Joining with any Sequence also returns a Sequence:
+        #   Tuple[int, bool] + List[bool] becomes Sequence[int]
+        if isinstance(self.s, TupleType):
+            if self.instance_joiner is None:
+                self.instance_joiner = InstanceJoiner()
+            fallback = self.instance_joiner.join_instances(
+                mypy.typeops.tuple_fallback(self.s), mypy.typeops.tuple_fallback(t)
+            )
+            assert isinstance(fallback, Instance)
+            items = self.join_tuples(self.s, t)
+            if items is not None:
+                if len(items) == 1 and isinstance(item := items[0], UnpackType):
+                    if isinstance(unpacked := get_proper_type(item.type), Instance):
+                        # Avoid double-wrapping tuple[*tuple[X, ...]]
+                        return unpacked
+                return TupleType(items, fallback)
+            else:
+                # TODO: should this be a default fallback behaviour like for meet?
+                if is_proper_subtype(self.s, t):
+                    return t
+                if is_proper_subtype(t, self.s):
+                    return self.s
+                return fallback
+        else:
+            return join_types(self.s, mypy.typeops.tuple_fallback(t))
+
+    def visit_typeddict_type(self, t: TypedDictType) -> ProperType:
+        if isinstance(self.s, TypedDictType):
+            items = {
+                item_name: s_item_type
+                for (item_name, s_item_type, t_item_type) in self.s.zip(t)
+                if (
+                    is_equivalent(s_item_type, t_item_type)
+                    and (item_name in t.required_keys) == (item_name in self.s.required_keys)
+                )
+            }
+            fallback = self.s.create_anonymous_fallback()
+            all_keys = set(items.keys())
+            # We need to filter by items.keys() since some required keys present in both t and
+            # self.s might be missing from the join if the types are incompatible.
+            required_keys = all_keys & t.required_keys & self.s.required_keys
+            # If one type has a key as readonly, we mark it as readonly for both:
+            readonly_keys = (t.readonly_keys | t.readonly_keys) & all_keys
+            return TypedDictType(items, required_keys, readonly_keys, fallback)
+        elif isinstance(self.s, Instance):
+            return join_types(self.s, t.fallback)
+        else:
+            return self.default(self.s)
+
+    def visit_literal_type(self, t: LiteralType) -> ProperType:
+        if isinstance(self.s, LiteralType):
+            if t == self.s:
+                return t
+            if self.s.fallback.type.is_enum and t.fallback.type.is_enum:
+                return mypy.typeops.make_simplified_union([self.s, t])
+            return join_types(self.s.fallback, t.fallback)
+        elif isinstance(self.s, Instance) and self.s.last_known_value == t:
+            return t
+        else:
+            return join_types(self.s, t.fallback)
+
+    def visit_partial_type(self, t: PartialType) -> ProperType:
+        # We only have partial information so we can't decide the join result. We should
+        # never get here.
+        assert False, "Internal error"
+
+    def visit_type_type(self, t: TypeType) -> ProperType:
+        if isinstance(self.s, TypeType):
+            return TypeType.make_normalized(
+                join_types(t.item, self.s.item),
+                line=t.line,
+                is_type_form=self.s.is_type_form or t.is_type_form,
+            )
+        elif isinstance(self.s, Instance) and self.s.type.fullname == "builtins.type":
+            return self.s
+        else:
+            return self.default(self.s)
+
+    def visit_type_alias_type(self, t: TypeAliasType) -> ProperType:
+        assert False, f"This should be never called, got {t}"
+
+    def default(self, typ: Type) -> ProperType:
+        typ = get_proper_type(typ)
+        if isinstance(typ, Instance):
+            return object_from_instance(typ)
+        elif isinstance(typ, TypeType):
+            return self.default(typ.item)
+        elif isinstance(typ, UnboundType):
+            return AnyType(TypeOfAny.special_form)
+        elif isinstance(typ, TupleType):
+            return self.default(mypy.typeops.tuple_fallback(typ))
+        elif isinstance(typ, TypedDictType):
+            return self.default(typ.fallback)
+        elif isinstance(typ, FunctionLike):
+            return self.default(typ.fallback)
+        elif isinstance(typ, TypeVarType):
+            return self.default(typ.upper_bound)
+        elif isinstance(typ, ParamSpecType):
+            return self.default(typ.upper_bound)
+        else:
+            return AnyType(TypeOfAny.special_form)
+
+
+def is_better(t: Type, s: Type) -> bool:
+    # Given two possible results from join_instances_via_supertype(),
+    # indicate whether t is the better one.
+    t = get_proper_type(t)
+    s = get_proper_type(s)
+
+    if isinstance(t, Instance):
+        if not isinstance(s, Instance):
+            return True
+        if t.type.is_protocol != s.type.is_protocol:
+            if t.type.fullname != "builtins.object" and s.type.fullname != "builtins.object":
+                # mro of protocol is not really relevant
+                return not t.type.is_protocol
+        # Use len(mro) as a proxy for the better choice.
+        if len(t.type.mro) > len(s.type.mro):
+            return True
+    return False
+
+
+def normalize_callables(s: ProperType, t: ProperType) -> tuple[ProperType, ProperType]:
+    if isinstance(s, (CallableType, Overloaded)):
+        s = s.with_unpacked_kwargs()
+    if isinstance(t, (CallableType, Overloaded)):
+        t = t.with_unpacked_kwargs()
+    return s, t
+
+
+def is_similar_callables(t: CallableType, s: CallableType) -> bool:
+    """Return True if t and s have identical numbers of
+    arguments, default arguments and varargs.
+    """
+    return (
+        len(t.arg_types) == len(s.arg_types)
+        and t.min_args == s.min_args
+        and t.is_var_arg == s.is_var_arg
+    )
+
+
+def is_similar_params(t: Parameters, s: Parameters) -> bool:
+    # This matches the logic in is_similar_callables() above.
+    return (
+        len(t.arg_types) == len(s.arg_types)
+        and t.min_args == s.min_args
+        and (t.var_arg() is not None) == (s.var_arg() is not None)
+    )
+
+
+def update_callable_ids(c: CallableType, ids: list[TypeVarId]) -> CallableType:
+    tv_map = {}
+    tvs = []
+    for tv, new_id in zip(c.variables, ids):
+        new_tv = tv.copy_modified(id=new_id)
+        tvs.append(new_tv)
+        tv_map[tv.id] = new_tv
+    return expand_type(c, tv_map).copy_modified(variables=tvs)
+
+
+def match_generic_callables(t: CallableType, s: CallableType) -> tuple[CallableType, CallableType]:
+    # The case where we combine/join/meet similar callables, situation where both are generic
+    # requires special care. A more principled solution may involve unify_generic_callable(),
+    # but it would have two problems:
+    #   * This adds risk of infinite recursion: e.g. join -> unification -> solver -> join
+    #   * Using unification is an incorrect thing for meets, as it "widens" the types
+    # Finally, this effectively falls back to an old behaviour before namespaces were added to
+    # type variables, and it worked relatively well.
+    max_len = max(len(t.variables), len(s.variables))
+    min_len = min(len(t.variables), len(s.variables))
+    if min_len == 0:
+        return t, s
+    new_ids = [TypeVarId.new(meta_level=0) for _ in range(max_len)]
+    # Note: this relies on variables being in order they appear in function definition.
+    return update_callable_ids(t, new_ids), update_callable_ids(s, new_ids)
+
+
+def join_similar_callables(t: CallableType, s: CallableType) -> CallableType:
+    t, s = match_generic_callables(t, s)
+    arg_types: list[Type] = []
+    for i in range(len(t.arg_types)):
+        arg_types.append(safe_meet(t.arg_types[i], s.arg_types[i]))
+    # TODO in combine_similar_callables also applies here (names and kinds; user metaclasses)
+    # The fallback type can be either 'function', 'type', or some user-provided metaclass.
+    # The result should always use 'function' as a fallback if either operands are using it.
+    if t.fallback.type.fullname == "builtins.function":
+        fallback = t.fallback
+    else:
+        fallback = s.fallback
+    return t.copy_modified(
+        arg_types=arg_types,
+        arg_names=combine_arg_names(t, s),
+        ret_type=join_types(t.ret_type, s.ret_type),
+        fallback=fallback,
+        name=None,
+    )
+
+
+def safe_join(t: Type, s: Type) -> Type:
+    # This is a temporary solution to prevent crashes in combine_similar_callables() etc.,
+    # until relevant TODOs on handling arg_kinds will be addressed there.
+    if not isinstance(t, UnpackType) and not isinstance(s, UnpackType):
+        return join_types(t, s)
+    if isinstance(t, UnpackType) and isinstance(s, UnpackType):
+        return UnpackType(join_types(t.type, s.type))
+    return object_or_any_from_type(get_proper_type(t))
+
+
+def safe_meet(t: Type, s: Type) -> Type:
+    # Similar to above but for meet_types().
+    from mypy.meet import meet_types
+
+    if not isinstance(t, UnpackType) and not isinstance(s, UnpackType):
+        return meet_types(t, s)
+    if isinstance(t, UnpackType) and isinstance(s, UnpackType):
+        unpacked = get_proper_type(t.type)
+        if isinstance(unpacked, TypeVarTupleType):
+            fallback_type = unpacked.tuple_fallback.type
+        elif isinstance(unpacked, TupleType):
+            fallback_type = unpacked.partial_fallback.type
+        else:
+            assert isinstance(unpacked, Instance) and unpacked.type.fullname == "builtins.tuple"
+            fallback_type = unpacked.type
+        res = meet_types(t.type, s.type)
+        if isinstance(res, UninhabitedType):
+            res = Instance(fallback_type, [res])
+        return UnpackType(res)
+    return UninhabitedType()
+
+
+def combine_similar_callables(t: CallableType, s: CallableType) -> CallableType:
+    t, s = match_generic_callables(t, s)
+    arg_types: list[Type] = []
+    for i in range(len(t.arg_types)):
+        arg_types.append(safe_join(t.arg_types[i], s.arg_types[i]))
+    # TODO kinds and argument names
+    # TODO what should happen if one fallback is 'type' and the other is a user-provided metaclass?
+    # The fallback type can be either 'function', 'type', or some user-provided metaclass.
+    # The result should always use 'function' as a fallback if either operands are using it.
+    if t.fallback.type.fullname == "builtins.function":
+        fallback = t.fallback
+    else:
+        fallback = s.fallback
+    return t.copy_modified(
+        arg_types=arg_types,
+        arg_names=combine_arg_names(t, s),
+        ret_type=join_types(t.ret_type, s.ret_type),
+        fallback=fallback,
+        name=None,
+    )
+
+
+def combine_arg_names(
+    t: CallableType | Parameters, s: CallableType | Parameters
+) -> list[str | None]:
+    """Produces a list of argument names compatible with both callables.
+
+    For example, suppose 't' and 's' have the following signatures:
+
+    - t: (a: int, b: str, X: str) -> None
+    - s: (a: int, b: str, Y: str) -> None
+
+    This function would return ["a", "b", None]. This information
+    is then used above to compute the join of t and s, which results
+    in a signature of (a: int, b: str, str) -> None.
+
+    Note that the third argument's name is omitted and 't' and 's'
+    are both valid subtypes of this inferred signature.
+
+    Precondition: is_similar_types(t, s) is true.
+    """
+    num_args = len(t.arg_types)
+    new_names = []
+    for i in range(num_args):
+        t_name = t.arg_names[i]
+        s_name = s.arg_names[i]
+        if t_name == s_name or t.arg_kinds[i].is_named() or s.arg_kinds[i].is_named():
+            new_names.append(t_name)
+        else:
+            new_names.append(None)
+    return new_names
+
+
+def object_from_instance(instance: Instance) -> Instance:
+    """Construct the type 'builtins.object' from an instance type."""
+    # Use the fact that 'object' is always the last class in the mro.
+    res = Instance(instance.type.mro[-1], [])
+    return res
+
+
+def object_or_any_from_type(typ: ProperType) -> ProperType:
+    # Similar to object_from_instance() but tries hard for all types.
+    # TODO: find a better way to get object, or make this more reliable.
+    if isinstance(typ, Instance):
+        return object_from_instance(typ)
+    elif isinstance(typ, (CallableType, TypedDictType, LiteralType)):
+        return object_from_instance(typ.fallback)
+    elif isinstance(typ, TupleType):
+        return object_from_instance(typ.partial_fallback)
+    elif isinstance(typ, TypeType):
+        return object_or_any_from_type(typ.item)
+    elif isinstance(typ, TypeVarLikeType) and isinstance(typ.upper_bound, ProperType):
+        return object_or_any_from_type(typ.upper_bound)
+    elif isinstance(typ, UnionType):
+        for item in typ.items:
+            if isinstance(item, ProperType):
+                candidate = object_or_any_from_type(item)
+                if isinstance(candidate, Instance):
+                    return candidate
+    elif isinstance(typ, UnpackType):
+        object_or_any_from_type(get_proper_type(typ.type))
+    return AnyType(TypeOfAny.implementation_artifact)
+
+
+def join_type_list(types: Sequence[Type]) -> Type:
+    if not types:
+        # This is a little arbitrary but reasonable. Any empty tuple should be compatible
+        # with all variable length tuples, and this makes it possible.
+        return UninhabitedType()
+    joined = types[0]
+    for t in types[1:]:
+        joined = join_types(joined, t)
+    return joined
+
+
+def unpack_callback_protocol(t: Instance) -> ProperType | None:
+    assert t.type.is_protocol
+    if t.type.protocol_members == ["__call__"]:
+        return get_proper_type(find_member("__call__", t, t, is_operator=True))
+    return None