type redefinition allowed when value coming from dictionary

[dpinol]

def kk(self, dic: Dict[str, str]) -> None:
  a = 2
  a = dic.get("as", "as2")

correctly complains that the type of a has changed:

error: Incompatible types in assignment (expression has type "Optional[str]", variable has type "int") [assignment]

However

def kk(self, dic: Dict) -> None:
       a = 2
       a = dic.get("as", "default")

does not complain that a type could be changed to str due to the default value in the get call.

Additionally, I'm not sure if the code below should complain since the dictionary may potentially return any type

def kk(self, dic: Dict) -> None:
       a = 2
       a = dic.get("as")

thanks!

[msullivan]

The last example is certainly correct behavior.

The main example is a little hairy. The cause here is that the typeshed stub for get is def get(self, k: _KT, default: Union[_VT_co, _T]) -> Union[_VT_co, _T]: ....
If we changed the definition to the more obvious def get(self, k: _KT, default: _T) -> Union[_VT_co, _T]: ..., then I think this would work. That change did get made, but we had to revert it because it caused issues python/typeshed#2817.

I think our conclusion was that #6613 would allow doing that. So I am going to close this issue in favor of that one but add a note to it. Thanks!

[dpinol]

thank you guys, mypy is amazing