Why are:
case ._:
not OK?
In this:
case .BLACK:
...
case BLACK:
...
the first matches the value against 'BLACK' and the second succeeds and
binds the value to 'BLACK'.
Replacing 'BLACK' with '_':
case ._:
...
case _:
...
I'd expect something similar, except for the binding part.
I think the same could be said for:
case Color.BLACK:
and:
case _.BLACK:
The PEP authors discussed this last night and (with a simple majority) we agreed that this restriction isn't all that important, so we're dropping it.
(We're considering other feedback carefully, but most of it require more deliberation.)