Pyright: Optional[T] of T never match `None`

[tamuhey]

I want to define the following unwrap function, which unwrap T from Optional[T].

from typing import Optional, TypeVar
T = TypeVar("T")
def unwrap(v: Optional[T]) -> T:
    if v is None:
        raise ValueError
    return v

However this unwrap doesn't work well with pyright, while it works well with mypy.

import random
def f() -> Optional[int]:
    return random.choice([0, None])
a: int = unwrap(f())  # Error: Type "None" cannot be assigned to type "int"

I think the cause is that pyright resolves T with Optional[int] instead of int.

I'm glad if pyright works well with this situation.

[erictraut]

Thanks for the bug report. I'm able to repro the problem, and I'll look into it.

[erictraut]

This will be fixed in the next published version of pyright. Thanks again for the bug report!

[erictraut]

This is fixed in 1.1.31, which I just published.