[issue31272] typing module conflicts with __slots__-classes

[Ilia Korvigo]

New submission from Ilia Korvigo:

I've got conflicts between Python's typing system and `__slots__`. Here is a small reproducible example.

    from typing import TypeVar, Generic, Sequence
    
    T = TypeVar("T")

    class TestGeneric(Sequence, Generic[T]):
        __slots__ = ("test",)

        def __init__(self, test: T):
            self.test = [test]
        
        def __iter__(self):
            return iter(self.test)
        def __len__(self):
            return len(self.test)
        
        def __contains__(self, item):
            return item in self.test
        
        def __getitem__(self, _):
            return self.test[0]

Now whenever I try to specify a content type, e.g.
    
    V = TestGeneric[int]

I get 

    ValueError: 'test' in __slots__ conflicts with class variable

I use `Generics`  in classes without slots a lot, hence I think this error has to be linked to `__slots__`. Moreover, the same class works fine, if you remove the `__slots__`

----------
components: Library (Lib)
messages: 300797
nosy: grayfall
priority: normal
severity: normal
status: open
title: typing module conflicts with  __slots__-classes
type: behavior
versions: Python 3.5

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue31272>
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