diff --git a/jedi/evaluate/__init__.py b/jedi/evaluate/__init__.py
index b69ca241..29d73818 100644
--- a/jedi/evaluate/__init__.py
+++ b/jedi/evaluate/__init__.py
@@ -266,7 +266,7 @@ class Evaluator(object):
         while parent is not None:
             parent = parent.parent
             predefined_if_name_dict = self.predefined_if_name_dict_dict.get(parent)
-            if predefined_if_name_dict:
+            if predefined_if_name_dict is not None:
                 return self._eval_element_not_cached(element)
         return self._eval_element_cached(element)
 
diff --git a/jedi/evaluate/helpers.py b/jedi/evaluate/helpers.py
index fd33e5c1..49edadbf 100644
--- a/jedi/evaluate/helpers.py
+++ b/jedi/evaluate/helpers.py
@@ -55,19 +55,14 @@ def deep_ast_copy(obj, parent=None, new_elements=None):
                     new_names_dict[string] = [new_elements[n] for n in names]
         return new_obj
 
-    if obj.type == 'name':
+    if isinstance(obj, tree.BaseNode):
+        new_obj = copy_node(obj)
+    else:
         # Special case of a Name object.
         new_elements[obj] = new_obj = copy.copy(obj)
-        if parent is not None:
-            new_obj.parent = parent
-    elif isinstance(obj, tree.BaseNode):
-        new_obj = copy_node(obj)
-        if parent is not None:
-            for child in new_obj.children:
-                if isinstance(child, (tree.Name, tree.BaseNode)):
-                    child.parent = parent
-    else:  # String literals and so on.
-        new_obj = obj  # Good enough, don't need to copy anything.
+
+    if parent is not None:
+        new_obj.parent = parent
     return new_obj
 
 
diff --git a/jedi/evaluate/iterable.py b/jedi/evaluate/iterable.py
index c6aafc91..b11b95a1 100644
--- a/jedi/evaluate/iterable.py
+++ b/jedi/evaluate/iterable.py
@@ -38,9 +38,9 @@ class IterableWrapper(tree.Base):
     @memoize_default()
     def _get_names_dict(self, names_dict):
         builtin_methods = {}
-        for cls in type(self).mro():
+        for cls in reversed(type(self).mro()):
             try:
-                builtin_methods = dict(builtin_methods, **cls.builtin_methods)
+                builtin_methods.update(cls.builtin_methods)
             except AttributeError:
                 pass
 
diff --git a/jedi/evaluate/representation.py b/jedi/evaluate/representation.py
index 82ba3e01..c460efd2 100644
--- a/jedi/evaluate/representation.py
+++ b/jedi/evaluate/representation.py
@@ -630,7 +630,9 @@ class FunctionExecution(Executed):
     def __init__(self, evaluator, base, *args, **kwargs):
         super(FunctionExecution, self).__init__(evaluator, base, *args, **kwargs)
         self._copy_dict = {}
-        new_func = helpers.deep_ast_copy(base.base_func, self, self._copy_dict)
+        new_func = helpers.deep_ast_copy(base.base_func, new_elements=self._copy_dict)
+        for child in new_func.children:
+            child.parent = self
         self.children = new_func.children
         self.names_dict = new_func.names_dict