Invalid Yield

What it does

Detects yield and yield from expressions where the "yield" or "send" type is incompatible with the generator function's annotated return type.

Why is this bad?

Yielding a value of a type that doesn't match the generator's declared yield type, or using yield from with a sub-iterator whose yield or send type is incompatible, is a type error that may cause downstream consumers of the generator to receive values of an unexpected type.

Examples

from typing import Iterator


def gen() -> Iterator[int]:
    yield "not an int"  # error: [invalid-yield]