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intentionally empty generator marked as unreachable #15345
Description
Bug Report
this seems to be a common pattern:
def f() -> Generator[None, None, None]:
return
yieldit can instead be rewritten as:
def f() -> Generator[None, None, None]:
yield from ()To Reproduce
see above
Expected Behavior
(no errors)
Actual Behavior
$ mypy --warn-unreachable t.py
t.py:5: error: Statement is unreachable [unreachable]
Found 1 error in 1 file (checked 1 source file)Your Environment
- Mypy version used: 1.3.0
- Mypy command-line flags:
--warn-unreachable - Mypy configuration options from
mypy.ini(and other config files): N/A - Python version used: 3.10.6
Activity
Hayashi-Yudai commentedon Jun 2, 2023
Uum... I couldn't reproduce this bug.
--warn-unreachableflagmypy.iniasottile commentedon Jun 2, 2023
yes you've used the workaround.
ikonst commentedon Jun 2, 2023
What could be a good heuristic here? That an empty yield statement (without expression) is explicitly allowed to trail a return statement?
asottile commentedon Jun 2, 2023
I'm not sure -- I think the only case is specifically the one in the issue -- I can't think of others since if it were conditional then there'd probably be a yield in the other arm. maybe this is specifically a cutout for
return; yieldas the total body?ikonst commentedon Jun 2, 2023
How about every function having a budget for one bare yield that doesn't get flagged?
ikonst commentedon Jun 7, 2023
Planning to address it on top of #15386.