Introduce py__next__ to have more clear way to use __next__

jedi/inference/base_value.py

@@ -175,6 +175,9 @@ class Value(HelperValueMixin):
                 message="TypeError: '%s' object is not iterable" % self)
         return iter([])
 
+    def py__next__(self, contextualized_node=None):
+        return self.py__iter__(contextualized_node)
+
     def get_signatures(self):
         return []
 

jedi/inference/value/instance.py

@@ -256,23 +256,23 @@ class _BaseTreeInstance(AbstractInstanceValue):
 
         def iterate():
             for generator in self.execute_function_slots(iter_slot_names):
-                if generator.is_instance() and not generator.is_compiled():
+                for lazy_value in generator.py__next__(contextualized_node):
+                    yield lazy_value
+        return iterate()
+
+    def py__next__(self, contextualized_node=None):
         # `__next__` logic.
         if self.inference_state.environment.version_info.major == 2:
             name = u'next'
         else:
             name = u'__next__'
-                    next_slot_names = generator.get_function_slot_names(name)
+        next_slot_names = self.get_function_slot_names(name)
         if next_slot_names:
             yield LazyKnownValues(
-                            generator.execute_function_slots(next_slot_names)
+                self.execute_function_slots(next_slot_names)
             )
         else:
-                        debug.warning('Instance has no __next__ function in %s.', generator)
-                else:
-                    for lazy_value in generator.py__iter__():
-                        yield lazy_value
-        return iterate()
+            debug.warning('Instance has no __next__ function in %s.', self)
 
     def py__call__(self, arguments):
         names = self.get_function_slot_names(u'__call__')

jedi/inference/value/iterable.py

@@ -23,6 +23,9 @@ from jedi.inference.value.dynamic_arrays import check_array_additions
 
 
 class IterableMixin(object):
+    def py__next__(self, contextualized_node=None):
+        return self.py__iter__(contextualized_node)
+
     def py__stop_iteration_returns(self):
         return ValueSet([compiled.builtin_from_name(self.inference_state, u'None')])
 
@@ -64,7 +67,7 @@ class GeneratorBase(LazyAttributeOverwrite, IterableMixin):
     @publish_method('send')
     @publish_method('next', python_version_match=2)
     @publish_method('__next__', python_version_match=3)
-    def py__next__(self, arguments):
+    def _next(self, arguments):
         return ValueSet.from_sets(lazy_value.infer() for lazy_value in self.py__iter__())
 
     def py__stop_iteration_returns(self):

jedi/plugins/stdlib.py

@@ -267,7 +267,7 @@ class ReversedObject(AttributeOverwrite):
 
     @publish_method('next', python_version_match=2)
     @publish_method('__next__', python_version_match=3)
-    def py__next__(self, arguments):
+    def _next(self, arguments):
         return ValueSet.from_sets(
             lazy_value.infer() for lazy_value in self._iter_list
         )