ClassVar should not allow TypeVar

[erictraut]

PEP 526 says:

Note that a ClassVar parameter cannot include any type variables, regardless of the level of nesting: ClassVar[T] and ClassVar[List[Set[T]]] are both invalid if T is a type variable.

See this issue in mypy issue tracker.

[hmc-cs-mdrissi]

I'm guessing the rule should also be extended to cover Paramspec/Typevartuple? The motivation seems like it applies for all generic parameters. Probably much rarer for the other two given usage frequency though.

[erictraut]

The next release will contain a new diagnostic check for a TypeVar used within ClassVar. It covers ParamSpec and TypeVarTuple as well. Internally, pyright treats these as special forms of TypeVar.

[erictraut]

This is addressed in pyright 1.1.188, which I just published. It will also be included in the next release of pylance.