Fix fast_parent_copy. The caching is now more solid than before (and doesn't produce weird side effects. This also solves an issue with Lambdas. However, by fixing all of this we have broken some other things.

jedi/evaluate/helpers.py

@@ -11,6 +11,7 @@ def fast_parent_copy(obj):
     """
     new_elements = {}
     accept = (pr.Simple, pr.NamePart)
+    start=obj
 
     def recursion(obj):
         if isinstance(obj, pr.Statement):
@@ -48,7 +49,7 @@ def fast_parent_copy(obj):
             elif isinstance(value, (list, tuple)):
                 setattr(new_obj, key, list_or_tuple_rec(value))
             elif isinstance(value, accept):
-                try:  # because of the circular Flow.previous/Flow.next
+                try:
                     setattr(new_obj, key, new_elements[value])
                 except KeyError:
                     setattr(new_obj, key, recursion(value))
@@ -61,7 +62,10 @@ def fast_parent_copy(obj):
             copied_array = array_obj[:]   # lists, tuples, strings, unicode
         for i, el in enumerate(copied_array):
             if isinstance(el, accept):
-                copied_array[i] = recursion(el)
+                try:
+                    copied_array[i] = new_elements[el]
+                except KeyError:
+                    copied_array[i] = recursion(el)
             elif isinstance(el, (tuple, list)):
                 copied_array[i] = list_or_tuple_rec(el)