"Yield value expected" on generator using send()

Bug Report

mypy doesn't allow empty yield statements in generator functions that accept send() values

To Reproduce

from typing import Any, Generator


def foo() -> Generator[int, Any, None]:
    yield
    while True:
        yield 42

Expected Behavior

I expected the second parameter (Any) in Generator[int, Any, None] to indicate that this generator accepts a send() value and that therefore the naked yield statement is accepting a value but not sending one. As far as I know the above code is idiomatic.

Actual Behavior

error: Yield value expected

mypy complains that a yield value is expected, but this standalone yield is for the purpose of accepting the value of a send() to the generator.

Your Environment

mypy 0.812
python 3.7

Empieza ejecutando el ejemplo de Python proporcionado con mypy y confirma el diagnóstico “Yield value expected”. Traza cómo mypy comprueba las sentencias yield de los generadores y el tipo send de Generator; se considera terminado cuando un yield sin expresión se acepta en este caso y el ejemplo cuenta con cobertura de regresión.