TEST: Add xfailing test for [func-returns-value]

[harahu]

Add an xfailing test that reproduces #14179.

[harahu]

Is there a canonical way to point back to the github issue from the test code, so that if the test passes at some point, it is easy to also close the issue?

[brianschubert]

Is there a canonical way to point back to the github issue from the test code, so that if the test passes at some point, it is easy to also close the issue?

I don't know about a canonical way, but any comment that points to the issue number / URL would probably be fine.
There's some existing test cases that do this in various ways.

[harahu]

Is there a canonical way to point back to the github issue from the test code, so that if the test passes at some point, it is easy to also close the issue?

I don't know about a canonical way, but any comment that points to the issue number / URL would probably be fine. There's some existing test cases that do this in various ways.

I added the URL as a comment.

[brianschubert]

I think this test would be better suited for check-expressions.test. There's a block of similar cases with the prefix testNoneReturn.

check-errorcodes.test is for tests related to error codes themselves.

[brianschubert]

This issue appear to affect any decorated function, so there may be value in including a test using an arbitrary dummy decorator, and with multiple levels of decoration.

For your consideration, please feel free to adapt as you see fit:

# test-data/unit/check-expressions.test
[case testNoneReturnDecorated]
from typing import Any, Callable, TypeVar

F = TypeVar('F', bound=Callable[..., Any])

def deco(f: F) -> F:
    pass

@deco
@deco
def f() -> None: 
    pass

class A:
    @staticmethod
    def s() -> None:
        pass

if int():
    x = f()      # E: "f" does not return a value (it only ever returns None)
if int():
    x = A.s()    # E: "s" of "A" does not return a value (it only ever returns None)
if int():
    x = A().s()  # E: "s" of "A" does not return a value (it only ever returns None)
[builtins fixtures/staticmethod.pyi]

[harahu]

I think this test would be better suited for check-expressions.test. There's a block of similar cases with the prefix testNoneReturn.

check-errorcodes.test is for tests related to error codes themselves.

Moved and renamed the test.

This issue appear to affect any decorated function, so there may be value in including a test using an arbitrary dummy decorator, and with multiple levels of decoration.

Good catch! I expanded the test based on your example.

EDIT: Also added an xfailing test for the __call__ method.

[brianschubert]

Nice

The __call__ case is interesting. There are some other tests that cover opaque callables in other kinds of expressions, like f = A(); y = f(). It seems that the relevant bit here is having the callee be a CallExpr

A few nits on the error messages:

[brianschubert]

LGTM

Both tests pass when I force all function calls to always return None.

[hauntsaninja]

Superseded by #18015