[ty] Do not carry the generic context of Protocol or Generic in the ClassBase enum (#17989)

## Summary

It doesn't seem to be necessary for our generics implementation to carry
the `GenericContext` in the `ClassBase` variants. Removing it simplifies
the code, fixes many TODOs about `Generic` or `Protocol` appearing
multiple times in MROs when each should only appear at most once, and
allows us to more accurately detect runtime errors that occur due to
`Generic` or `Protocol` appearing multiple times in a class's bases.

In order to remove the `GenericContext` from the `ClassBase` variant, it
turns out to be necessary to emulate
`typing._GenericAlias.__mro_entries__`, or we end up with a large number
of false-positive `inconsistent-mro` errors. This PR therefore also does
that.

Lastly, this PR fixes the inferred MROs of PEP-695 generic classes,
which implicitly inherit from `Generic` even if they have no explicit
bases.

## Test Plan

mdtests
This commit is contained in:
Alex Waygood 2025-05-22 21:37:03 -04:00 committed by GitHub
parent 6c0a59ea78
commit d02c9ada5d
No known key found for this signature in database
GPG key ID: B5690EEEBB952194
15 changed files with 271 additions and 215 deletions

View file

@ -83,7 +83,7 @@ python-version = "3.9"
```py
class A(tuple[int, str]): ...
# revealed: tuple[<class 'A'>, <class 'tuple[@Todo(Generic tuple specializations), ...]'>, <class 'Sequence[@Todo(Generic tuple specializations)]'>, <class 'Reversible[@Todo(Generic tuple specializations)]'>, <class 'Collection[@Todo(Generic tuple specializations)]'>, <class 'Iterable[@Todo(Generic tuple specializations)]'>, <class 'Container[@Todo(Generic tuple specializations)]'>, typing.Protocol[_T_co], typing.Generic[_T_co], <class 'object'>]
# revealed: tuple[<class 'A'>, <class 'tuple[@Todo(Generic tuple specializations), ...]'>, <class 'Sequence[@Todo(Generic tuple specializations)]'>, <class 'Reversible[@Todo(Generic tuple specializations)]'>, <class 'Collection[@Todo(Generic tuple specializations)]'>, <class 'Iterable[@Todo(Generic tuple specializations)]'>, <class 'Container[@Todo(Generic tuple specializations)]'>, typing.Protocol, typing.Generic, <class 'object'>]
reveal_type(A.__mro__)
```
@ -114,6 +114,6 @@ from typing import Tuple
class C(Tuple): ...
# revealed: tuple[<class 'C'>, <class 'tuple[Unknown, ...]'>, <class 'Sequence[Unknown]'>, <class 'Reversible[Unknown]'>, <class 'Collection[Unknown]'>, <class 'Iterable[Unknown]'>, <class 'Container[Unknown]'>, typing.Protocol[_T_co], typing.Generic[_T_co], <class 'object'>]
# revealed: tuple[<class 'C'>, <class 'tuple[Unknown, ...]'>, <class 'Sequence[Unknown]'>, <class 'Reversible[Unknown]'>, <class 'Collection[Unknown]'>, <class 'Iterable[Unknown]'>, <class 'Container[Unknown]'>, typing.Protocol, typing.Generic, <class 'object'>]
reveal_type(C.__mro__)
```