Return type of unbound methods of generic types incorrectly inferred.

[jonathanslenders]

Bug Report
Consider the following snippet:

from typing import Generic, TypeVar

T = TypeVar("T")


class Base(Generic[T]):
    def f(self) -> _T: ...


class Child(Base[bool]):
    ...


# Following three lines demonstrate two issues:
# - `T` was never filled in.
# - The return type became `Any`.

# test.py:21: note: Revealed type is "def (self: a.Base[T`1]) -> Any"
# test.py:22: note: Revealed type is "def [T] (self: a.Base[T`1]) -> Any"
# test.py:23: note: Revealed type is "def (self: a.Base[T`1]) -> Any"
reveal_type(Child.f)
reveal_type(Base.f)  # In this case, probably expected.
reveal_type(Base[int].f)

# When calling the unbound method, the return type is `Any`.
unbound_method = Child.f
x = unbound_method(Base())
reveal_type(x)  # Any.

Expected Behavior

I'd expect the typevar to be replaced.

Your Environment

• Mypy version used: 0.982
• Python version used: 3.9.13

[ilevkivskyi]

This is not a bug, you have an extra underscore in _T, and mypy clearly says:

error: Name "_T" is not defined

(there is unrelated small thing that is wrong here, but this is duplicated in other issues).