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Resolve TypeVar upper bounds in functools.partial
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Mostly fixes python#17646
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hauntsaninja committed Aug 10, 2024
1 parent 8b74b5a commit 85f0682
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2 changes: 2 additions & 0 deletions mypy/checker.py
Original file line number Diff line number Diff line change
Expand Up @@ -682,6 +682,8 @@ def extract_callable_type(self, inner_type: Type | None, ctx: Context) -> Callab
inner_type = get_proper_type(inner_type)
outer_type: CallableType | None = None
if inner_type is not None and not isinstance(inner_type, AnyType):
if isinstance(inner_type, TypeVarLikeType):
inner_type = inner_type.upper_bound
if isinstance(inner_type, TypeType):
if isinstance(inner_type.item, Instance):
inner_type = expand_type_by_instance(
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11 changes: 11 additions & 0 deletions test-data/unit/check-functools.test
Original file line number Diff line number Diff line change
Expand Up @@ -541,3 +541,14 @@ p(1, "no") # E: Argument 2 to "A" has incompatible type "str"; expected "int"

q: partial[A] = partial(A, 1) # OK
[builtins fixtures/tuple.pyi]

[case testFunctoolsPartialTypeVarBound]
from typing import Callable, TypeVar
import functools

T = TypeVar("T", bound=Callable[[str, int], str])

def foo(f: T) -> T:
g = functools.partial(f, "foo")
return f
[builtins fixtures/tuple.pyi]

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