Incorrect type parameter scope inference with nested classes

[jonathandung]

Bug Report

In a class whose body is nested in another, mypy doesn't recognize the type parameters of the outer class as bound in the inner.

To Reproduce

# test_mypy.py
class Foo[T]:
    class Bar[R]:
        def foobar(self, t: T, r: R, /) -> None: ...
        print(T, R)

Output of program

T R

Note that there is no NameError being thrown. The names T and R are indeed both bound in the scope of the definition of R.

Actual Behavior

test_mypy.py:3: error: Name "T" is not defined  [name-defined]
Found 1 error in 1 file (checked 1 source file)

Your Environment

• Mypy version used:
• Command used: mypy test_mypy.py
• Mypy configuration options from mypy.ini (and other config files): None relevant
• Python version used: 3.12, 3.13, 3.14