[ty] Minor fixes to Protocol tests#20347
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AlexWaygood
added
testing
| # this is fine: the call succeeds at runtime since the second argument is optional | ||
| reveal_type(len(SecondOptionalArgument())) # revealed: Literal[0] |
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we could consider emitting a diagnostic on the definition of __len__ itself here (but that should be a disabled-by-default lint rule, IMO!), but I see no reason why we should emit a diagnostic at the len() call itself here. SecondOptionalArgument is a subtype of Sized.
| class CanIndex(Protocol[T]): | ||
| def __getitem__(self, index: int) -> T: ... | ||
| def __getitem__(self, index: int, /) -> T: ... |
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The intent of this test is that list[str] should be a subtype of CanIndex; below, an instance of list[str] is passed into takes_in_protocol. But as written, list[str] is not a subtype of CanIndex, since all parameters of list.__getitem__ are positional-only
| Because method members are always looked up on the meta-type of an object when testing assignability | ||
| and subtyping, we understand that `IterableClass` here is a subtype of `Iterable` even though | ||
| `Foo.__iter__` resolves to a type with the wrong signature: | ||
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| ```py | ||
| from typing import Iterator, Iterable | ||
| from ty_extensions import static_assert, is_subtype_of, TypeOf | ||
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| class Meta(type): | ||
| def __iter__(self) -> Iterator[int]: | ||
| yield from range(42) | ||
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| class IterableClass(metaclass=Meta): | ||
| def __iter__(self) -> Iterator[str]: | ||
| yield from "abc" | ||
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| static_assert(is_subtype_of(TypeOf[IterableClass], Iterable[int])) | ||
| ``` |
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A missing test that demonstrates another reason why it's important that dunder methods especially must be looked up on the meta-type when determining protocol subtyping/assignability
AlexWaygood
requested review from
carljm,
dcreager and
sharkdp
as code owners
Co-authored-by: Carl Meyer <[email protected]>
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