[Bug] Using filter in itertools.chain makes them both infer wrong types.

[Jackenmen]

Repro:

import itertools
from typing import List

x: List[int] = [1, 2, 3]
y: List[str] = ["  ", "", "abc"]


it = itertools.chain(x, filter(lambda s: s.strip() == "", y))
reveal_type(it)

Actual output:

main.py:8: error: "object" has no attribute "strip"
main.py:9: note: Revealed type is 'itertools.chain[builtins.object*]'

Expected output:
I was expecting no errors and didn't expect filter to be affected by what it is put in, i.e. if you put filter call separate from itertools.chain, it prevents the first errors about missing strip attr:

f = filter(lambda s: s.strip() == "", y)
it = itertools.chain(x, f)
reveal_type(it)

The revealed type is still wrong though.

---

Python version: 3.7.6
Mypy version: 0.760 (still occurs on master)
Used flags: --strict