[Regression 1.6.x -> 1.7] Invalid "Returning Any from function declared..."

To Reproduce

from __future__ import annotations
from functools import partialmethod
import operator
from typing import Any, Union

ScalarType = Union[int, bool, float]
ArrayOrScalar = Union["Array", ScalarType]


class Array:
    def _binary_op(self,
            op: Any,
            other: ArrayOrScalar,
            ) -> Array:

        return Array()

    __mul__ = partialmethod(_binary_op, operator.mul)


def dot(a: ArrayOrScalar, b: ArrayOrScalar) -> ArrayOrScalar:
    assert isinstance(a, Array)
    assert isinstance(b, Array)

    return a * b

Expected Behavior

Type-checks correctly, as it does with 1.6.1.

Actual Behavior

/home/andreas/tmp/mypy-array-repro.py:30: error: Returning Any from function declared to return "Array | int | bool | float"  [no-any-return]
Found 1 error in 1 file (checked 1 source file)

Your Environment

• Mypy version used: 1.7.0 (compiled: yes)
• Mypy command-line flags: --strict
• Mypy configuration options from mypy.ini (and other config files): none
• Python version used: 3.12

Start by running the supplied reproducer with mypy 1.7.0 and --strict, then compare its result with mypy 1.6.1. Trace how the type checker handles Array._binary_op, partialmethod, and operator.mul; done means the example no longer reports no-any-return while preserving the expected return type.