None cannot be assigned to typing.Hashable

[layday]

Describe the bug
None cannot be assigned to typing.Hashable. None is hashable in Python.

To Reproduce
Type check the snippet below.

Expected behavior
That None would be accepted as a value of type Hashable.

Screenshots or Code

from typing import Dict, Hashable

# Expression of type "None" cannot be assigned to declared type "Hashable"
#   Type "None" cannot be assigned to type "Hashable"
foo: Hashable = None

# Expression of type "dict[None, str]" cannot be assigned to declared type "Dict"
#   TypeVar "_KT" is invariant
#     Type "None" cannot be assigned to type "Hashable"
bar: Dict[Hashable, str] = {None: ''}

# True
isinstance(None, Hashable)

VS Code extension or command-line
Extension, 1.1.65

[erictraut]

I'm not convinced this is a bug in pyright. Mypy also reports errors the same errors.

Maybe the builtins.pyi typeshed stub should define a NoneType that defines the methods that the NoneType class supports.

I'll need to think about this more.

[layday]

NoneType is not in builtins however. The only way to access NoneType in Python is by calling type on None. Even then perhaps it could be stubbed out for the benefit of type checkers.

[erictraut]

I've submitted a PR to typeshed to add a _NoneType class to typing.pyi. Once that's incorporated, I can add support for this feature.

[erictraut]

The PR was accepted to typeshed, so this is now unblocked.

[erictraut]

This is now addressed in Pyright 1.1.74, which I just published. It will also be included in the next release of Pylance.