removed caching for subexpr attributes as it can break tree manipulation

Cython/Compiler/ExprNodes.py

@@ -196,7 +196,6 @@ class ExprNode(Node):
     def subexpr_nodes(self):
         #  Extract a list of subexpression nodes based
         #  on the contents of the subexprs class attribute.
-        if self.saved_subexpr_nodes is None:
         nodes = []
         for name in self.subexprs:
             item = getattr(self, name)
@@ -205,8 +204,7 @@ class ExprNode(Node):
                     nodes.append(item)
                 else:
                     nodes.extend(item)
-            self.saved_subexpr_nodes = nodes
-        return self.saved_subexpr_nodes
+        return nodes
         
     def result(self):
         if not self.is_temp or self.is_target: