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ilevkivskyiilevkivskyi
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Fix crash on typevar with forward ref used in other module (#20334)
Fixes #20326 Type variables with forward references in upper bound are known to be problematic. Existing mechanisms to work with them implicitly assumed that they are used in the same module where they are defined, which is not necessarily the case for "old-style" type variables that can be imported. Note that the simplification I made in `semanal_typeargs.py` would be probably sufficient to fix this, but that would be papering over the real issue, so I am making a bit more principled fix.
1 parent 67df116 commit 25cf74b

5 files changed

Lines changed: 105 additions & 9 deletions

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‎mypy/plugins/proper_plugin.py‎

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@@ -108,6 +108,7 @@ def is_special_target(right: ProperType) -> bool:
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"mypy.types.RequiredType",
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"mypy.types.ReadOnlyType",
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"mypy.types.TypeGuardedType",
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"mypy.types.PlaceholderType",
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):
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# Special case: these are not valid targets for a type alias and thus safe.
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# TODO: introduce a SyntheticType base to simplify this?

‎mypy/semanal.py‎

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@@ -4945,7 +4945,7 @@ def get_typevarlike_argument(
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)
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if analyzed is None:
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# Type variables are special: we need to place them in the symbol table
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# soon, even if upper bound is not ready yet. Otherwise avoiding
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# soon, even if upper bound is not ready yet. Otherwise, avoiding
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# a "deadlock" in this common pattern would be tricky:
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# T = TypeVar('T', bound=Custom[Any])
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# class Custom(Generic[T]):

‎mypy/semanal_typeargs.py‎

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@@ -176,12 +176,12 @@ def validate_args(
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code=codes.VALID_TYPE,
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)
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continue
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if self.in_type_alias_expr and isinstance(arg, TypeVarType):
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# Type aliases are allowed to use unconstrained type variables
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# error will be checked at substitution point.
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continue
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if tvar.values:
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if isinstance(arg, TypeVarType):
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if self.in_type_alias_expr:
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# Type aliases are allowed to use unconstrained type variables
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# error will be checked at substitution point.
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continue
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arg_values = arg.values
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if not arg_values:
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is_error = True
@@ -205,10 +205,6 @@ def validate_args(
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and upper_bound.type.fullname == "builtins.object"
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)
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if not object_upper_bound and not is_subtype(arg, upper_bound):
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if self.in_type_alias_expr and isinstance(arg, TypeVarType):
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# Type aliases are allowed to use unconstrained type variables
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# error will be checked at substitution point.
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continue
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is_error = True
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self.fail(
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message_registry.INVALID_TYPEVAR_ARG_BOUND.format(

‎mypy/typeanal.py‎

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@@ -346,6 +346,15 @@ def visit_unbound_type_nonoptional(self, t: UnboundType, defining_literal: bool)
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if hook is not None:
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return hook(AnalyzeTypeContext(t, t, self))
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tvar_def = self.tvar_scope.get_binding(sym)
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if tvar_def is not None:
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# We need to cover special-case explained in get_typevarlike_argument() here,
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# since otherwise the deferral will not be triggered if the type variable is
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# used in a different module. Using isinstance() should be safe for this purpose.
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tvar_params = [tvar_def.upper_bound, tvar_def.default]
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if isinstance(tvar_def, TypeVarType):
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tvar_params += tvar_def.values
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if any(isinstance(tp, PlaceholderType) for tp in tvar_params):
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self.api.defer()
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if isinstance(sym.node, ParamSpecExpr):
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if tvar_def is None:
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if self.allow_unbound_tvars:

‎test-data/unit/check-type-aliases.test‎

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@@ -1351,3 +1351,93 @@ reveal_type(D(x="asdf")) # E: No overload variant of "dict" matches argument ty
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# N: def __init__(self, arg: Iterable[tuple[str, int]], **kwargs: int) -> dict[str, int] \
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# N: Revealed type is "Any"
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[builtins fixtures/dict.pyi]
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[case testTypeAliasesInCyclicImport1]
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import p.aliases
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[file p/__init__.py]
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[file p/aliases.py]
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from typing_extensions import TypeAlias
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from .defs import C, Alias1
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Alias2: TypeAlias = Alias1[C]
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[file p/defs.py]
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from typing import TypeVar
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from typing_extensions import TypeAlias
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import p.aliases
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C = TypeVar("C", bound="SomeClass")
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Alias1: TypeAlias = C
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class SomeClass:
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pass
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[builtins fixtures/tuple.pyi]
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[typing fixtures/typing-full.pyi]
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[case testTypeAliasesInCyclicImport2]
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import p.aliases
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[file p/__init__.py]
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[file p/aliases.py]
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from typing_extensions import TypeAlias
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from .defs import C, Alias1
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Alias2: TypeAlias = Alias1[C]
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[file p/defs.py]
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from typing import TypeVar, Union
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from typing_extensions import TypeAlias
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import p.aliases
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C = TypeVar("C", bound="SomeClass")
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Alias1: TypeAlias = Union[C, int]
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class SomeClass:
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pass
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[builtins fixtures/tuple.pyi]
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[case testTypeAliasesInCyclicImport3]
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import p.aliases
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[file p/__init__.py]
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[file p/aliases.py]
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from typing_extensions import TypeAlias
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from .defs import C, Alias1
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Alias2: TypeAlias = Alias1[C]
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[file p/defs.py]
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from typing import TypeVar
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from typing_extensions import TypeAlias
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import p.aliases
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C = TypeVar("C", bound="list[SomeClass]")
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Alias1: TypeAlias = C
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class SomeClass:
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pass
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[builtins fixtures/tuple.pyi]
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[typing fixtures/typing-full.pyi]
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[case testTypeAliasesInCyclicImport4]
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import p.aliases
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[file p/__init__.py]
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[file p/aliases.py]
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from typing_extensions import TypeAlias
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from .defs import C, Alias1
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Alias2: TypeAlias = Alias1[C]
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[file p/defs.py]
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from typing import TypeVar, Union
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from typing_extensions import TypeAlias
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import p.aliases
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C = TypeVar("C", bound="list[SomeClass]")
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Alias1: TypeAlias = Union[C, int]
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class SomeClass:
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pass
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[builtins fixtures/tuple.pyi]

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