Allow dict to take a Generator

[tekumara]

from typing import Dict

d: Dict[str,str] = dict(token.split('=', 1) for token in ['a=b'])

Fails in mypy 0.782 with:

test/test.py:3: error: Generator has incompatible item type "List[str]"; expected "Tuple[str, str]"

And in pyright 1.1.62 with:

3:20 - error: No overloads for "dict(token.split('=', 1) for token in ['a=b'])" match parameters
  Argument types: (Generator[List[str]]) (reportGeneralTypeIssues)

[tekumara]

Related #257

[tekumara]

Converting to a tuple:

d: Dict[str,str] = dict(tuple(token.split('=', 1)) for token in ['a=b'])

Produces:

test/test.py:3: error: Generator has incompatible item type "Tuple[str, ...]"; expected "Tuple[str, str]"

[JelleZijlstra]

This isn't anything to do with generators; the issue is that .split() returns a list, and mypy doesn't know that the list has exactly two items, so it doesn't let you pass it to the dict. python/mypy#7509 has some previous discussion.

[tekumara]

Thanks for the pointer @JelleZijlstra I'll add # type: ignore for now.