Incompatible definition of methods reported when using multiple inheritance

[frerich]

Using mypy 0.782, errors about incompatible method redefinitions are issued -- but only if multiple inheritance is in play.

How to Reproduce

Run mypy (without any arguments) on this script:

import enum

class C:
    pass

class D(C, enum.IntFlag):
    pass

Expected behaviour

mypy should print

Success: no issues found in 1 source file

Actual behaviour

mypy prints three error messages:

mypy-error.py:6: error: Definition of "__xor__" in base class "int" is incompatible with definition in base class "Flag"
mypy-error.py:6: error: Definition of "__or__" in base class "int" is incompatible with definition in base class "Flag"
mypy-error.py:6: error: Definition of "__and__" in base class "int" is incompatible with definition in base class "Flag"
Found 3 errors in 1 file (checked 1 source file)

Comments

The error messages go away when

• Not using multiple inheritance, i.e. class D(enum.IntFlag) instead of class D(C, enum.IntFlag).
• Or: when using enum.Flag instead of enum.IntFlag

[JukkaL]

This looks like a bug in type checking classes with multiple inheritance. You can use # type: ignore on line 6 as a workaround for now.

[adambirds]

Is this related to this issue here? Is there any idea when a proper fix will be available?

[benbovy]

Is there any update on this?

Alternatively to adding # type: ignore, another workaround is to redefine the problematic methods in the subclass with a simple call to super. That's not pretty either but that prevents ignoring the whole inheritance.