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[red-knot] GenericAlias instances as a base class (#17575)

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## Summary

We currently emit a diagnostic for code like the following:
```py
from typing import Any

# error: Invalid class base with type `GenericAlias` (all bases must be a class, `Any`, `Unknown` or `Todo`)
class C(tuple[Any, ...]): ...
```

The changeset here silences this diagnostic by recognizing instances of
`GenericAlias` in `ClassBase::try_from_type`, and inferring a `@Todo`
type for them. This is a change in preparation for #17557, because `C`
previously had `Unknown` in its MRO …
```py
reveal_type(C.__mro__)  # tuple[Literal[C], Unknown, Literal[object]]
```
… which would cause us to think that `C` is assignable to everything.

The changeset also removes some false positive `invalid-base`
diagnostics across the ecosystem.

## Test Plan

Updated Markdown tests.
This commit is contained in:
David Peter
2025-04-23 10:39:10 +02:00
committed by GitHub
parent 3fae176345
commit b1b8ca3bcd
5 changed files with 8 additions and 11 deletions
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6
crates/red_knot_python_semantic/resources/mdtest/annotations/stdlib_typing_aliases.md
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@@ -106,13 +106,13 @@ reveal_type(ChainMapSubclass.__mro__)
class CounterSubclass(typing.Counter): ...
# TODO: Should be (CounterSubclass, Counter, dict, MutableMapping, Mapping, Collection, Sized, Iterable, Container, Generic, object)
# revealed: tuple[Literal[CounterSubclass], Literal[Counter], Unknown, Literal[object]]
# revealed: tuple[Literal[CounterSubclass], Literal[Counter], @Todo(GenericAlias instance), @Todo(`Generic[]` subscript), Literal[object]]
reveal_type(CounterSubclass.__mro__)
class DefaultDictSubclass(typing.DefaultDict): ...
# TODO: Should be (DefaultDictSubclass, defaultdict, dict, MutableMapping, Mapping, Collection, Sized, Iterable, Container, Generic, object)
# revealed: tuple[Literal[DefaultDictSubclass], Literal[defaultdict], Unknown, Literal[object]]
# revealed: tuple[Literal[DefaultDictSubclass], Literal[defaultdict], @Todo(GenericAlias instance), Literal[object]]
reveal_type(DefaultDictSubclass.__mro__)
class DequeSubclass(typing.Deque): ...
@@ -124,6 +124,6 @@ reveal_type(DequeSubclass.__mro__)
class OrderedDictSubclass(typing.OrderedDict): ...
# TODO: Should be (OrderedDictSubclass, OrderedDict, dict, MutableMapping, Mapping, Collection, Sized, Iterable, Container, Generic, object)
# revealed: tuple[Literal[OrderedDictSubclass], Literal[OrderedDict], Unknown, Literal[object]]
# revealed: tuple[Literal[OrderedDictSubclass], Literal[OrderedDict], @Todo(GenericAlias instance), Literal[object]]
reveal_type(OrderedDictSubclass.__mro__)
```