Feature request: implicit-flag-overlap

[jayaddison]

Current problem

The following behaviour seemed confusing:

>>> from enum import IntFlag
>>> class TestFlag(IntFlag):
...     A = 1
...     B = 2
...     C = 3
... 
>>> print([i for i in TestFlag])
[<TestFlag.A: 1>, <TestFlag.B: 2>]

(note that this is an IntFlag, not an IntEnum)

Desired solution

The reason this happens is that Flag types are designed for setwise operations (bitwise operations, in the case of IntFlag), and, because C can be composed of A and B...

>>> int(TestFlag.A | TestFlag.B)
3
>>> int(TestFlag.C)
3

...internally, IntFlag considers C to be an alias -- and doesn't include it when iterating over the members of the flag.

A pylint message something along the lines of implicit-flag-overlap could be emitted by a relevant checker when scanning the class declaration.

Additional context

No response