Bare ClassVar should infer type instead of defaulting to Any

[ilevkivskyi]

Currently we have:

from typing import ClassVar
  
class C:
    x: ClassVar = 1

reveal_type(C.x)  # Revealed type is 'Any'

ClassVar is not a generic type (and not really a type, rather an access qualifier). So it will be better if a bare ClassVar would use inference instead of defaulting to Any thus reducing verbosity or false negatives (although --disallow-any-generics actually flags this).

Probably not high priority.

[gvanrossum]

I agree. Should this become an update to PEP 526?

[ilevkivskyi]

Should this become an update to PEP 526?

I think it is worth explicitly mentioning it in the PEP.

[gvanrossum]

OK, but is it still provisional? It was provisionally accepted for 3.6. Can we still change it? (PEP 411 suggests provisional applies to a single feature release.)

[ilevkivskyi]

Hm, this is a good question. I think PEP 484 stayed provisional longer than that, so there is a precedent. Also this is not runtime-affecting thing, so I would say this is OK.

[gvanrossum]

Fair enough.

[Avasam]

This is now part of the typing spec:

• Typing specification update: Allow bare typing.ClassVar qualifiers typing-council#43
• https://typing.python.org/en/latest/spec/class-compat.html#classvar