Closed
Description
Issue description
This doesn't generate an error:
# test_case7.py
from typing import List
def untyped_func_def_with_typed_body():
a: List[int] = [0, 1, 2]
key: str = "asdf"
a[key] # <- No error, despite internals being typedThis does:
# test_case8.py
from typing import List
def typed_func_def_with_typed_body() -> None:
a: List[int] = [0, 1, 2]
key: str = "asdf"
a[key] # <- *Now* this generates an errorThat maybe technically "documented", but that's really esoteric and completely unintuitive. I've spent hours chasing this down.
Archived original flailing to arrive at core problem
UPDATE 2: Okay, this just keeps getting weirder and weirder. Consider:
# test_case3.py
def func():
a = [0, 1, 2]
a["asdf"] # <- This doesn't generate an error
b = [0, 1, 2]
b["asdf"] # <- But this does?!Runtime:
% mypy --config=/dev/null test_case3.py
/dev/null: No [mypy] section in config file
test_case3.py:8: error: No overload variant of "__getitem__" of "list" matches argument type "str"
test_case3.py:8: note: Possible overload variants:
test_case3.py:8: note: def __getitem__(self, SupportsIndex) -> int
test_case3.py:8: note: def __getitem__(self, slice) -> List[int]
Found 1 error in 1 file (checked 1 source file)
UPDATE 1: You don't need the @overloads. It still doesn't work without them. Here's the simplified case:
# test_case2.py
from typing import List, Union
class GetItemTest:
def __getitem__(self, key: Union[int, slice]) -> Union[int, List[int]]:
return list(range(10))[key]
def test_a():
a = GetItemTest()
a["asdf"] # <- Why isn't this a typing error?Original case (same effect):
# test_case1.py
from typing import List, Union, overload
class GetItemTest:
@overload
def __getitem__(self, key: int) -> int:
...
@overload
def __getitem__(self, key: slice) -> List[int]:
...
def __getitem__(self, key: Union[int, slice]) -> Union[int, List[int]]:
return list(range(10))[key]
def test_a():
a = GetItemTest()
a["asdf"] # <- Why isn't this a typing error?Runtime:
% python --version
Python 3.9.6
% pip list
Package Version
----------------- --------
mypy 0.910
mypy-extensions 0.4.3
pip 21.2.1
setuptools 57.4.0
toml 0.10.2
typing-extensions 3.10.0.0
% mypy --version
mypy 0.910
% mypy --config=/dev/null test_case1.py
/dev/null: No [mypy] section in config file
Success: no issues found in 1 source file
I can't prove it, but I feel like this used to work. It seems pretty basic.