17.3.0 cmp/default/hash/WeakKeyDictionary interaction #289

On 17.3.0, an @attr.s(hash=False) class which has an attr.ib with a @default that looks itself up in a WeakKeyDictionary into which it has previously been placed by an earlier @default raises an AttributeError on construction, unless @attr.s(cmp=False) is also set.

This worked properly on 17.2.0.

import attr
import weakref
bugs = weakref.WeakKeyDictionary()

@attr.s(hash=False)
class Bug(object):
    a = attr.ib()
    @a.default
    def make_a(self):
        bugs[self] = 1
        return 1

    b = attr.ib()
    @b.default
    def make_b(self):
        bugs[self]
        return 2

Bug()