TypeVar bound not respected in Generic class method overloads

Bug Report

Mypy chooses the wrong overload of a generic class method in the below code. str | Sequence[int] would match Sequence[ItemT] if ItemT was not bounded or constrained, but since it is constrained to non-str the overload for str | Sequence[ItemT] should be matched instead. The issue only affects generic class methods and not regular functions.

To Reproduce

from collections.abc import Sequence
from typing import Generic, TypeVar, overload

from typing_extensions import assert_type


T = TypeVar("T", covariant=True)
ItemT = TypeVar("ItemT", bound=int)  # OR TypeVar("ItemT", int, float)


class MyGeneric(Generic[T]):
    @overload
    def transform(self: "MyGeneric[str]") -> "MyGeneric[str]": ...

    @overload
    def transform(self: "MyGeneric[Sequence[ItemT]]") -> "MyGeneric[Sequence[ItemT]]": ...

    @overload
    def transform(self: "MyGeneric[str | Sequence[ItemT]]") -> "MyGeneric[str | Sequence[ItemT]]": ...

    def transform(self: "MyGeneric[str | Sequence[ItemT]]") -> "MyGeneric[str | Sequence[ItemT]]": ...  # type: ignore


assert_type(MyGeneric[str]().transform(), MyGeneric[str])
assert_type(MyGeneric[Sequence[int]]().transform(), MyGeneric[Sequence[int]])
assert_type(MyGeneric[str | Sequence[int]]().transform(), MyGeneric[str | Sequence[int]])
# error: Expression is of type "MyGeneric[Sequence[object]]", not "MyGeneric[str | Sequence[int]]"

# ---
# The equivalent functions do not have the same issue

@overload
def transform(x: "MyGeneric[str]") -> "MyGeneric[str]": ...

@overload
def transform(x: "MyGeneric[Sequence[ItemT]]") -> "MyGeneric[Sequence[ItemT]]": ...

@overload
def transform(x: "MyGeneric[str | Sequence[ItemT]]") -> "MyGeneric[str | Sequence[ItemT]]": ...

def transform(x: "MyGeneric[str | Sequence[ItemT]]") -> "MyGeneric[str | Sequence[ItemT]]": ...  # type: ignore


assert_type(transform(MyGeneric[str]()), MyGeneric[str])
assert_type(transform(MyGeneric[Sequence[int]]()), MyGeneric[Sequence[int]])
assert_type(transform(MyGeneric[str | Sequence[int]]()), MyGeneric[str | Sequence[int]])

Your Environment

• Mypy version used: 1.14.1
• Mypy command-line flags:
• Mypy configuration options from mypy.ini (and other config files):
• Python version used: 3.13.0

Start by running the supplied reproduction with mypy 1.14.1 and confirming the incorrect assert_type result for the generic class method. Trace overload resolution for generic class methods, then add or update coverage so the bound or constrained TypeVar selects the expected overload while the equivalent functions remain correct.