Forward-referencing type application with type variable in a value expression in stubs emits confusing error

Bug Report, To Reproduce, & Actual Behaviour

In .pyi stub files, the spec mandates type-checkers to recognise forward references in annotation expressions without string-quoting. It is however silent about value expressions, but in mypy I've used symbols defined later in a stub file in a value context before without any issues, except recently when hitting the following example:

# stub.pyi
from typing_extensions import Generic, TypeVar

R = TypeVar("R")
T = TypeVar("T")

class A(Generic[R]):
    var = B[R]()  # E: "R" is a type variable and only valid in type context

class B(Generic[T]): ...

Expected Behavior

Either:

1. no errors, or
2. mypy doesn't support forward references in value contexts for stub files, and this emits a used-before-def error at B[R]().

Your Environment

• Mypy version used: 1.17
• Python version used: 3.11, 3.12

Commencez par le reproducteur stub.pyi et examinez la manière dont mypy gère les références anticipées dans les expressions de valeur des fichiers stub. Comparez le diagnostic actuel aux deux résultats attendus décrits dans l’issue ; c’est terminé lorsque le comportement est soit accepté, soit signalé comme used-before-def à B[R]().