Closed as not planned
Description
Bug Report
When using yield from to return an Iterator of any generics mypy fails to identify the type and falls back to object unless a Union is involved.
To Reproduce
Using list[...] as example. Behavior is the same with custom Generics.
from __future__ import annotations
from typing import Any, Iterator
l_int: list[int] = [1, 2]
l_str: list[str]
l_str = ["a", "b"]
l_union: list[str] | list[bytes]
l_union = ["a", "b"]
def iter_yield() -> Iterator[list[Any]]:
yield l_int
yield l_str # this passes
def iter_yield_from() -> Iterator[list[Any]]:
reveal_type(l_int) # builtins.list[builtins.int]
reveal_type(l_str) # builtins.list[builtins.str]
reveal_type(l_union) # Union[builtins.list[builtins.str], builtins.list[builtins.bytes]]
yield from (
l_int,
l_str,
) # error: Incompatible types in "yield from" (actual type "object", expected type "List[Any]")
yield from (
l_int,
l_str,
l_union,
) # error: Incompatible types in "yield from" (actual type "object", expected type "List[Any]")
yield from (
l_int,
l_union,
l_str,
) # union on first or second position passes 🙃Expected Behavior
I'd expect to infer the type to list[Any] or list[str | int] for yield from ( l_int, l_str,).
Actual Behavior
(Write what happened.)
Your Environment
- Mypy version used: 0.812
- Mypy command-line flags: none
- Mypy configuration options from
mypy.ini(and other config files):
# setup.cfg
[mypy]
python_version = 3.8
strict = true
warn_unreachable = true
implicit_reexport = true
ignore_missing_imports = true
- Python version used: 3.9.1
- Operating system and version: macOS 10.13.6