Check attributes for variance violations #735

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1. JukkaL

   added

   feature

   on Aug 9, 2015
2. jhance commented on Oct 11, 2015

   

   jhance

   on Oct 11, 2015

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   I wonder if theres a way to word the error message here so it would be the same as #734?
3. JukkaL commented on Oct 12, 2015

   

   JukkaL

   on Oct 12, 2015

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   Hmm.. can't come up with a good common message right now. Why not just come up with a separate message for attributes?
4. JukkaL commented on Oct 12, 2015

   

   JukkaL

   on Oct 12, 2015

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   Also, assignment to a covariant attribute should be rejected. There doesn't seem to be issue for that.
5. JukkaL

   added

   topic-type-variables

   priority-1-normal

   bugmypy got something wrongmypy got something wrong

   and removed

   feature

   on May 18, 2018
6. KotlinIsland commented on Feb 2, 2023

   

   KotlinIsland

   on Feb 2, 2023

   Last edited by KotlinIsland

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   Am I correct in thinking that an example of this issue is:

   from typing import TypeVar, Generic
   T = TypeVar("T", covariant=True)
   class Foo(Generic[T]):
       foo: T
   a: Foo[int] = Foo()
   b: Foo[object] = a
   b.foo = "sus"
   a.foo + 1  # no mypy error, runtime error