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Include tuple fallback in constraints built from tuple types #19100

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Include tuple fallback in constraints built from tuple types #19100

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59f8e25
Include fallback in building constraints for tuple types
sterliakov May 17, 2025
8b23cf0
Add a testcase
sterliakov May 17, 2025
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5 changes: 5 additions & 0 deletions mypy/constraints.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1335,6 +1335,11 @@ def visit_tuple_type(self, template: TupleType) -> list[Constraint]:
res.extend(
infer_constraints(template_items[i], actual_items[i], self.direction)
)
res.extend(
infer_constraints(
template.partial_fallback, actual.partial_fallback, self.direction
)
)
return res
elif isinstance(actual, AnyType):
return self.infer_against_any(template.items, actual)
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16 changes: 16 additions & 0 deletions test-data/unit/check-typevar-tuple.test
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Expand Up @@ -2628,3 +2628,19 @@ def fn(f: Callable[[*tuple[T]], int]) -> Callable[[*tuple[T]], int]: ...
def test(*args: Unpack[tuple[T]]) -> int: ...
reveal_type(fn(test)) # N: Revealed type is "def [T] (T`1) -> builtins.int"
[builtins fixtures/tuple.pyi]

[case testConstraintsIncludeTupleFallback]
from typing import Generic, TypeVar
from typing_extensions import TypeVarTuple, Unpack

T = TypeVar("T")
Ts = TypeVarTuple("Ts")
_FT = TypeVar("_FT", bound=type)

def identity(smth: _FT) -> _FT:
return smth

@identity
class S(tuple[Unpack[Ts]], Generic[T, Unpack[Ts]]):
def f(self, x: T, /) -> T: ...
[builtins fixtures/tuple.pyi]