fix Class.interfaces so that no InferenceError raised on empty __implements__

--HG--
branch : stable

1 files changed, 3 insertions, 1 deletions

diff --git a/scoped_nodes.py b/scoped_nodes.py
index d6595b28..b53ec4e5 100644
--- a/scoped_nodes.py
+++ b/scoped_nodes.py
@@ -927,13 +927,15 @@ class Class(StmtMixIn, LocalsDictNodeNG, FilterStmtsMixin):
         if not herited and not implements.frame() is self:
             return
         found = set()
+        missing = False
         for iface in unpack_infer(implements):
             if iface is YES:
+                missing = True
                 continue
             if not iface in found and handler_func(iface):
                 found.add(iface)
                 yield iface
-        if not found:
+        if missing:
             raise InferenceError()