Incorrect error when using sum

[yhenon]

The following sample code shows mypy generating an error when using python's built-in sum(). As far as I can tell, there should be no error here, as dividing an int and a float is valid behavior. This can also be seen by the fact that assigning to an intermediary variable suppresses the error.

from typing import List

X: List[float] = [1.]
B = sum(X)

print(1 / B)       # no error
print(1 / sum(X))  # error: Argument 1 to "sum" has incompatible type "List[float]"; expected "Iterable[int]"

python 3.6.8, mypy version 0.740

[samsont]

I ran into the same issue. Interestingly, I found that if the numerator is a float, there is also no error. Adding to the above code:

print(1.0 / sum(X)) # no error

[samsont]

I think this may be the same as ticket #6040

[ilevkivskyi]

Yes, this is a duplicate of #6040