Try to introduce is_instance and is_function

jedi/evaluate/context/function.py

@@ -75,6 +75,9 @@ class FunctionContext(use_metaclass(CachedMetaClass, AbstractFunction)):
     """
     Needed because of decorators. Decorators are evaluated here.
     """
+    def is_function(self):
+        return True
+
     @classmethod
     def from_context(cls, context, tree_node):
         def create(tree_node):
@@ -92,12 +95,10 @@ class FunctionContext(use_metaclass(CachedMetaClass, AbstractFunction)):
                     tree_node=tree_node
                 )
 
-        from jedi.evaluate.context import AbstractInstanceContext
-
         overloaded_funcs = list(_find_overload_functions(context, tree_node))
 
         parent_context = context
-        while parent_context.is_class() or isinstance(parent_context, AbstractInstanceContext):
+        while parent_context.is_class() or parent_context.is_instance():
             parent_context = parent_context.parent_context
 
         function = create(tree_node)

jedi/evaluate/context/instance.py

@@ -68,8 +68,8 @@ class AbstractInstanceContext(Context):
         self.class_context = class_context
         self.var_args = var_args
 
-    def is_class(self):
-        return False
+    def is_instance(self):
+        return True
 
     def get_annotated_class_object(self):
         return self.class_context  # This is the default.
@@ -114,7 +114,7 @@ class AbstractInstanceContext(Context):
         # `method` is the new parent of the array, don't know if that's good.
         names = self.get_function_slot_names(u'__get__')
         if names:
-            if isinstance(obj, AbstractInstanceContext):
+            if obj.is_instance():
                 return self.execute_function_slots(names, obj, obj.class_context)
             else:
                 none_obj = compiled.builtin_from_name(self.evaluator, u'None')
@@ -156,7 +156,7 @@ class AbstractInstanceContext(Context):
             return
 
         for generator in self.execute_function_slots(iter_slot_names):
-            if isinstance(generator, AbstractInstanceContext):
+            if generator.is_instance():
                 # `__next__` logic.
                 if self.evaluator.environment.version_info.major == 2:
                     name = u'next'