Fix stub function inferrals

jedi/evaluate/context/instance.py

@@ -283,7 +283,7 @@ class TreeInstance(AbstractInstanceContext):
                 continue
 
             all_annotations = py__annotations__(execution.tree_node)
-            defined = self.class_context.define_generics(
+            defined, = self.class_context.define_generics(
                 infer_type_vars_for_execution(execution, all_annotations),
             )
             debug.dbg('Inferred instance context as %s', defined, color='BLUE')

jedi/evaluate/context/klass.py

@@ -272,11 +272,11 @@ class ClassContext(use_metaclass(CachedMetaClass, ClassMixin, FunctionAndClassBa
                 yield type_var_dict.get(type_var.py__name__(), NO_CONTEXTS)
 
         if type_var_dict:
-            return GenericClass(
+            return ContextSet([GenericClass(
                 self,
                 generics=tuple(remap_type_vars())
-            )
-        return self
+            )])
+        return ContextSet({self})
 
     def get_signatures(self):
         init_funcs = self.py__getattribute__('__init__')