Fix an edge case: make providedBy() work when a class has '__provides__' in

its __slots__ (see http://thread.gmane.org/gmane.comp.web.zope.devel/22490)

1 files changed, 3 insertions, 1 deletions

diff --git a/src/zope/interface/declarations.py b/src/zope/interface/declarations.py
index 3bc28a7..44a40e2 100644
--- a/src/zope/interface/declarations.py
+++ b/src/zope/interface/declarations.py
@@ -31,6 +31,7 @@ __docformat__ = 'restructuredtext'
 import sys
 import weakref
 from zope.interface.interface import InterfaceClass, Specification
+from zope.interface.interface import SpecificationBase
 from ro import mergeOrderings, ro
 import exceptions
 from types import ClassType, ModuleType
@@ -1248,7 +1249,8 @@ def getObjectSpecification(ob):
 
     provides = getattr(ob, '__provides__', None)
     if provides is not None:
-        return provides
+        if isinstance(provides, SpecificationBase):
+            return provides
 
     try:
         cls = ob.__class__