yield from inside list comprehension gives wrong type

[Akuli]

Bug Report

runtime and mypy types don't match, possibly related to #6457

To Reproduce

from typing import Generator

def f() -> Generator[int, None, str]:
    yield 1
    return "lol"

def g() -> Generator[int, None, None]:
    x = [(yield from f()) for lel in range(5)]
    print(x)        # <generator object g.<locals>.<listcomp> at 0x7fba92696a20>
    reveal_type(x)  # List[str]

g()

Expected Behavior

reveal_type outputting Generator[something] to match runtime

Actual Behavior

List[str]

Your Environment

• Mypy version used: 0.812
• Mypy command-line flags: none
• Mypy configuration options from mypy.ini (and other config files): none
• Python version used: 3.7.3

[JelleZijlstra]

Similar to my comment in #10189, this was made a SyntaxError in 3.8 because the runtime behavior made little sense. It doesn't seem worth the effort to try to match the runtime behavior in mypy for 3.6/3.7, but maybe we can emit an error and infer Any.

[erictraut]

Mypy correctly flags the use of yield within a list comprehension as an error, consistent with Python 3.8 and newer. Now that 3.7 support in mypy has been deprecated, this issue can safely be closed.

[hauntsaninja]

Technically mypy's only dropped support for running with 3.7, not necessarily type checking targeting 3.7. But agreed this should be closed