Pyright does not respect `__class_getitem__` annotations.

[imgurbot12]

Describe the bug

Pyright does not seem to respect type-annotations defined by custom __class_getitem__ implementations.

It assumes the getitem will return the associated class type regardless of the annotations present.

Code or Screenshots

from typing import Annotated, TypeVar, cast, reveal_type

T = TypeVar('T')

class Foo:
    @classmethod
    def __class_getitem__(cls, type: T) -> T:
        return cast(T, Annotated[type, cls()])

foo = Foo[str]
reveal_type(foo) # Type of "foo" is "type[Foo]"

In the example above the type should report as str.

VS Code extension or command-line

This issue exists both in LSP and with the latest version of the pyright command-line v1.1.411

[imgurbot12]

Interestingly enough, it works with a metaclass __getitem__ but not with a standard __class_getitem__ but only sometimes since it raises an error if the type annotation is defined inside a function:

from typing import Annotated, TypeVar, cast, get_args, reveal_type

T = TypeVar('T')

class Meta(type):
    def __getitem__(self, type: T) -> T:
        return cast(T, Annotated[type, self()])

class Foo(metaclass=Meta):
    pass

foo = Foo[str]
reveal_type(foo) # Type of "foo" is "type[str]"

def bar(a: Foo[int]): # error: Expected no type arguments for class "Foo"
    pass

[imgurbot12]

Same if you declare a typealias, which I assume is the same error when defining it inside a function.

Test: TypeAlias = Foo[str] # error: Expected no type arguments for class "Foo"

[jorenham]

Related discussion: https://discuss.python.org/t/should-non-generic-classes-with-class-getitem-be-subscriptable-in-a-type-expression/108666