[question] dictionary _KT typevar and hashability

[BvB93]

Dear all,

I recently noticed that the _KT typevar used in annotating dict has no upper bound specified, yet dictionary keys must (as far as I'm aware) always be hashable.

Is there a reason here as to why _KT is not defined as TypeVar('_KT', bound=Hashable)?

Regards, Bas

[JelleZijlstra]

The Hashable type can't really be typechecked (because all types are hashable by default); see prior discussion in #2148, python/mypy#1746, python/mypy#2455.

[BvB93]

Thanks for the info!
I'd consider this question answered.

[ikonst]

Given that certain types are marked as non-hashable (#3219) wouldn't this have at least a fringe value?