Optimized version of InterfaceBase doesn't use interface's __adapt__

[Ben Artin]

According to zope.interface documentation, the __call__ of an interface should use __adapt__ in the interface to attempt to adapt the object. This is not so with the optimized C version of InterfaceBase:

from zope.interface import Interface
class Test(Interface):
    pass
def adapt(*args, **kwargs):
    return 17
from new import instancemethod
Test.__adapt__ = instancemethod(adapt, Test)
print Test.__adapt__(1) # prints 17
Test(1) # Generates an exception

This is not how InterfaceBasePy.__call__ behaves -- it uses interface.__adapt__, which can be customized for each interface. This discrepancy between InterfaceBasePy and the C-optimized InterfaceBase should be eliminated; I believe that the behavior of InterfaceBase should change to match that of InterfaceBasePy.

[Christian Theune (ctheune)]

__adapt__ is not documented in IInterface. However, the tests say that we do this and respect PEP 246 behaviour.

[Tres Seaver (tseaver)]

Please follow-up on Github:

  https://github.com/zopefoundation/zope.interface/issues/3