Incompatible return value type when using typevar with bound and self returning method

[CaselIT]

Bug Report

Using a typevar bound to a class that has a self returning method leads to an error when using in a function that operates on the typevar and returns the typevar. Using constraint does not present the issue but looses the generic on the class.

To Reproduce

# pyright: strict
from typing import Any, Generic, TypeVar
from typing_extensions import Self, reveal_type

T = TypeVar("T")


class X(Generic[T]):
    def m(self, v: int) -> Self:
        return self

class Y:
    def m(self, v: int) -> Self:
        return self

# using bound: tb_self errors with Incompatible return value type
TB = TypeVar("TB", bound=X[Any] | Y)

def tb_self(value: TB) -> TB:
    return value.m(42)

def tb(value: TB) -> TB:
    return value

reveal_type(tb_self(X[int]()))
reveal_type(tb(X[int]()))

# using constraint: return type is X[Any] in both cases
TC = TypeVar("TC", X[Any], Y)

def tc_self(value: TC) -> TC:
    return value.m(42)

def tc(value: TC) -> TC:
    return value

reveal_type(tc_self(X[int]()))
reveal_type(tc(X[int]()))

https://gist.github.com/mypy-play/3f911f7de9e2282fb6463a7146ffae47

The output is:

file.py:20:12: error: Incompatible return value type (got "X[Any] | Y", expected "TB")  [return-value]
file.py:25:13: note: Revealed type is "try_.X[builtins.int]"
file.py:26:13: note: Revealed type is "try_.X[builtins.int]"
file.py:37:13: note: Revealed type is "try_.X[Any]"
file.py:38:13: note: Revealed type is "try_.X[Any]"
Found 1 error in 1 file (checked 1 source file)

For reference pyright on the same input reports no error

Expected Behavior

The is no error.

Actual Behavior

Mypy reports an error when the using a self returning method

Your Environment

• Mypy version used: 1.9.0, 1.7.1
• Mypy command-line flags: none
• Mypy configuration options from mypy.ini (and other config files): -
• Python version used: 3.10, 3.12