Type hint defaults don't work with inheritance

[leezu]

Consider

In [12]: @attr.s(auto_attribs=True)
    ...: class A:
    ...:     a: int = 10
    ...:

In [13]: @attr.s(auto_attribs=True)
    ...: class B(A):
    ...:     pass
    ...:

In [14]: A()
Out[14]: A(a=10)

In [15]: B()
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-15-1c5ecc61f85b> in <module>()
----> 1 B()

TypeError: __init__() missing 1 required positional argument: 'a'

This should work, given that the following works:

In [16]: @attr.s()
    ...: class A:
    ...:     a = attr.ib(default=10)
    ...:

In [17]: @attr.s()
    ...: class B(A):
    ...:     pass
    ...:

In [18]: A()
Out[18]: A(a=10)

In [19]: B()
Out[19]: B(a=10)

[hynek]

Ugh so it’s not inheritance, it’s inheritance + no new annotations. The problem is that __annotations__ gets inherited:

>>> import attr

>>> @attr.s(auto_attribs=True)
... class A:
...     a: int = 10

>>> @attr.s(auto_attribs=True)
... class B(A):
...     pass

>>> A.__annotations__
{'a': <class 'int'>}

>>> B.__annotations__
{'a': <class 'int'>}

>>> A.__annotations__ is B.__annotations__
True

>>> @attr.s(auto_attribs=True)
... class C(A):
...     c: float = 20.0

>>> C()
C(a=10, c=20.0)