Incompatible dictionary results in confusing error message

[JukkaL]

Dictionary literals with incompatible keys/values result in weird error message, because mypy translate the expression internally to something quite different before type checking.

from typing import Dict
d = {1 : ''} # type: Dict[int, int]

This gives a confusing error message:

t2.py:2: error: List item 0 has incompatible type "Tuple[int, str]"

[fabianhjr]

Ok, this has to do with mypy/messages.py:466: msg = '{} item {} has incompatible type {}'.format(; I will take a look at it. The only thing is that about 20 test cases will need to be changed.

[fabianhjr]

Ok, so this is what I have in mind:

Test if we are dealing with a List[Tuple[Any, Any]] and if so add * NOTE: This might be a Dict to the error message.

Additionally, also add the expected type.

[fabianhjr]

Ok, a fix/imrpovement is ready; It should now read:

t2.py:2: error: List item 0 has incompatible type "Tuple[int, str]"; expected "Tuple[int, int]" * NOTE: This might be a Dict[K, V] instead of List[Tuple[K, V]]

Could you tell me if this is clearer @JukkaL ?

[JukkaL]

Fixed by #3100.