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Fix false negatives involving Unions and generators or coroutines #14224

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Merged
hauntsaninja merged 2 commits into from
Dec 1, 2022
Merged

Fix false negatives involving Unions and generators or coroutines #14224

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8276f7b
Fix unexpected Any when awaiting a union
hauntsaninja Nov 30, 2022
80cc4e0
add test for generator union
hauntsaninja Dec 1, 2022
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12 changes: 12 additions & 0 deletions mypy/checker.py
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Original file line number Diff line number Diff line change
Expand Up @@ -843,6 +843,10 @@ def get_generator_yield_type(self, return_type: Type, is_coroutine: bool) -> Typ

if isinstance(return_type, AnyType):
return AnyType(TypeOfAny.from_another_any, source_any=return_type)
elif isinstance(return_type, UnionType):
return make_simplified_union(
[self.get_generator_yield_type(item, is_coroutine) for item in return_type.items]
)
elif not self.is_generator_return_type(
return_type, is_coroutine
) and not self.is_async_generator_return_type(return_type):
Expand Down Expand Up @@ -873,6 +877,10 @@ def get_generator_receive_type(self, return_type: Type, is_coroutine: bool) -> T

if isinstance(return_type, AnyType):
return AnyType(TypeOfAny.from_another_any, source_any=return_type)
elif isinstance(return_type, UnionType):
return make_simplified_union(
[self.get_generator_receive_type(item, is_coroutine) for item in return_type.items]
)
elif not self.is_generator_return_type(
return_type, is_coroutine
) and not self.is_async_generator_return_type(return_type):
Expand Down Expand Up @@ -912,6 +920,10 @@ def get_generator_return_type(self, return_type: Type, is_coroutine: bool) -> Ty

if isinstance(return_type, AnyType):
return AnyType(TypeOfAny.from_another_any, source_any=return_type)
elif isinstance(return_type, UnionType):
return make_simplified_union(
[self.get_generator_return_type(item, is_coroutine) for item in return_type.items]
)
elif not self.is_generator_return_type(return_type, is_coroutine):
# If the function doesn't have a proper Generator (or
# Awaitable) return type, anything is permissible.
Expand Down
18 changes: 18 additions & 0 deletions test-data/unit/check-async-await.test
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Expand Up @@ -925,3 +925,21 @@ async def f() -> AsyncGenerator[int, None]:

[builtins fixtures/async_await.pyi]
[typing fixtures/typing-async.pyi]

[case testAwaitUnion]
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@JukkaL JukkaL Nov 30, 2022

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Does this also fix type checking yield in generators? If yes, can you add a test case for this?

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@hauntsaninja hauntsaninja Dec 1, 2022

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Yeah it does, will do!

from typing import overload, Union

class A: ...
class B: ...

@overload
async def foo(x: A) -> B: ...
@overload
async def foo(x: B) -> A: ...
async def foo(x): ...

async def bar(x: Union[A, B]) -> None:
reveal_type(await foo(x)) # N: Revealed type is "Union[__main__.B, __main__.A]"

[builtins fixtures/async_await.pyi]
[typing fixtures/typing-async.pyi]
⚡