typechecked methods of generics do not check typed iterators.

[erp12]

I think this might be an impossible issue to fix because Python iterators (and all other standard collections) can hold elements of multiple types. Feel free to close without much consideration.

If I have a class that extends generic and has a method that takes an iterator, I cannot type check that the iterator has all elements of the desired type. This arises in the use case of creating a typed list which supports extend.

from typing import TypeVar, Generic, Iterator
from pytypes import typechecked

T = TypeVar('T')

class TypList(Generic[T], list):

    @typechecked
    def append(self, obj: T) -> None:
        super().append(obj)

    @typechecked
    def extend(self, iterable: Iterator[T]) -> None:
        super().extend(iterable)

    @typechecked
    def insert(self, index: int, obj: T) -> None:
        super().insert(index, obj)

class IntList(TypList[int]):
    ...

il = IntList() 

il.append(1) # No error, as expected
il.append("a") # InputTypeError as expected

il.extend(iter([1, 2, 3])) # No error, as expected
il.extend(iter(["a", "b", "c"])) # No error, somewhat unexpected

print(il) # [1, 1, 2, 3, 'a', 'b', 'c']  <-- Ideally would only hold ints

In this case, a perfectly reasonable workaround is the check the contents of iterable manually, not using the decorator.

[Stewori]

I am implementing a fix that wraps iterables and iterators into little typecheckers.
For cases where this is too invasive, one can opt out via pytypes.check_iterables = False.