Make classes with __getitem__ work in for context #10386
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sobolevn
reviewed
Dec 9, 2021
| @@ -3499,20 +3500,40 @@ def analyze_iterable_item_type(self, expr: Expression) -> Tuple[Type, Type]: | |||
| """Analyse iterable expression and return iterator and iterator item types.""" | |||
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Let's explain how iterables are handled in CPython. Priorities and possibilities.
| return self.named_generic_type("typing.Iterator", [getitem_type]), getitem_type | ||
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| self.msg.add_errors(iter_msg_builder) | ||
| # Non-tuple iterable. |
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This comment does not really explain what is going on anymore.
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| if not getitem_msg_builder.is_errors(): | ||
| # We found __getitem__ | ||
| return self.named_generic_type("typing.Iterator", [getitem_type]), getitem_type |
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Looks like it should be typing.Iterable and not Iterator.
| @@ -1940,6 +1940,17 @@ reveal_type(list(c for c in C)) # N: Revealed type is "builtins.list[__main__.C | |||
| reveal_type(list(C)) # N: Revealed type is "builtins.list[__main__.C*]" | |||
| [builtins fixtures/list.pyi] | |||
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| [case testIterableGetItemOnClass] | |||
| class A: | |||
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Let's also test:
- Metaclasses with
__getitem__and__class_getitem__ forstatementslist(iter(A()))andlist(iter(B()))
sobolevn
reviewed
Dec 9, 2021
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| if iter_msg_builder.is_errors(): | ||
| # We couldn't find __iter__ so let's try __getitem__ | ||
| getitem_msg_builder = temp_message_builder() |
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You can try to use .clean_copy() here.
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Description
The for analysis searches for iter to decide if it is iterable. I've added a search for getitem as well.
This is a step in the right direction for #2220 but it doesn't really make classes with getitem be accepted as arguments marked as Iterable - I'm not sure how to solve this without being intrusive in either typeshed or mypy type inference.
Please note that I've made it work with getitem that accepts int (as the docs say) so if you have only getitem with string, this will generate an error.
Test Plan
I've added a few tests and mypy primer seems to have fewer errors :)