MyPy checks fail when overriding __eq__ to return a custom type and calling it as a right-operator

[migwellian]

When I override __eq__ and return a custom type, the MyPy checks succeed when my custom type is on the LHS of the equality, but fail when my custom type is on the RHS of the equality.

Here is an example to illustrate: line 14 yields no error but line 16 yields an error:

Incompatible types in assignment (expression has type "bool", variable has type "MyClass")

from typing import Any


class MyClass:

    def __eq__(self, other: Any) -> 'MyClass':
        return self


def test_tmp() -> None:
    x = MyClass()
    y = 1.
    result: MyClass
    result = (x == y)
    assert type(result) == MyClass
    result = (y == x)
    assert type(result) == MyClass

The test passes, i.e. I get back an object of type MyClass when x is on the LHS or RHS of my equality.

NB - there is also a MyPy error on line 6, Return type of "__eq__" incompatible with supertype "object" - this is because of #2783. I think my issue is separate from this one.

Version numbers: Python 3.6.5, mypy 0.641.