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

Beginne damit, die bereitgestellte Reproduktion mit mypy 1.14.1 auszuführen und das falsche assert_type-Ergebnis für die generische Klassenmethode zu bestätigen. Verfolge anschließend die Überladungsauflösung für generische Klassenmethoden und füge Tests hinzu oder aktualisiere die Testabdeckung so, dass der gebundene oder eingeschränkte TypeVar die erwartete Überladung auswählt, während die entsprechenden Funktionen weiterhin korrekt funktionieren.