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Invalid definition of Tuple in return reports on a confusing line number #3177
Description
Here's an example:
class TestTuple:
@staticmethod
def test(a: str) -> (bool, str):
return len(a) < 2, a[:2]
And here's the output (I'd expect it to say Line #3):
test_invalid_tuple.py:2: error: Invalid tuple literal type
Activity
ilevkivskyi commentedon Apr 14, 2017
This may be because mypy's parser considers decorator a part of the function definition and assigns the function type the first line of the function definition.
daveisfera commentedon Apr 14, 2017
Yes, I assumed that that was the case but for someone like me that's new to typing in Python and using mypy to verify it, it was confusing. Now that I now that you're supposed to do
Tuple(bool, str)and that(bool, str)is invalid I would know how to fix it. But it took me a few minutes of thinking "there's not even a tuple on that line" before I realized what I was supposed to do.On a related note, it is also confusing that you can't using the normal tuple syntax for typing.
gvanrossum commentedon Apr 15, 2017
Yes, that's why, and I agree it would be better to pin-point errors to the specific line where they occur.
Presuming you're referring to the idea of writing
(int, str)instead ofTuple[int, str], that ship has sailed -- there are some edge cases here that wouldn't work well (unfortunately I don't have time to rehash the discussion, it's probably in one of the mega-threads we had in 2014/2015 about PEP 484.patrickw276 commentedon May 22, 2017
I'm going to take a stab at this issue.
Use argument and return type line numbers for error messages (#3395)