Mypy does not correctly understand MemberDescriptors for objects with slots.

Bug Report

When a Python object uses slots, MemberDescriptors are created for each attribute defined as a slot.

Mypy incorrectly interprets these fields as the type of the slotted value, rather than as a member descriptor.

To Reproduce

class TestObject(object):
   __slots__ = ["a", "b"]
   a: int
   b: str

   def __init__(self, a: int, b: str) -> None:
      self.a = a
      self.b = b

def test() -> None:
   x = TestObject(5, "hi")
   reveal_type(TestObject.a)
   reveal_type(TestObject.b)
   reveal_type(x.a)
   reveal_type(x.b)

Expected Behavior

Here is what the types actually are based on the python repl.

>>> TestObject
<class '__main__.TestObject'>
>>> x = TestObject(10, "hi")
>>> type(TestObject.a)
<class 'member_descriptor'>
>>> type(TestObject.b)
<class 'member_descriptor'>
>>> type(x.a)
<class 'int'>
>>> type(x.b)
<class 'str'>

Actual Behavior

Mypy output:
12: note: Revealed type is 'builtins.int'
13: note: Revealed type is 'builtins.str'
14: note: Revealed type is 'builtins.int'
15: note: Revealed type is 'builtins.str'

Your Environment

Python 3.8.1
mypy 0.782

Start with the provided slots and MemberDescriptor reproduction, then trace how mypy determines the types revealed for class attributes versus instance attributes. Confirm the fix by checking that TestObject.a and TestObject.b are reported as member descriptors while x.a and x.b remain int and str.