support non-trivial counter targets for enumerate() loop optimisation

Cython/Compiler/Optimize.py

@@ -523,9 +523,6 @@ class IterationTransform(Visitor.EnvTransform):
         if len(targets) != 2:
             # leave this untouched for now
             return node
-        if not isinstance(targets[0], ExprNodes.NameNode):
-            # leave this untouched for now
-            return node
 
         enumerate_target, iterable_target = targets
         counter_type = enumerate_target.type

tests/run/enumerate_T316.pyx

@@ -14,6 +14,19 @@ def go_py_enumerate():
     for i,k in enumerate(range(1,5)):
         print i, k
 
+@cython.test_fail_if_path_exists("//SimpleCallNode//NameNode[@name = 'enumerate']")
+def py_enumerate_list_index_target():
+    """
+    >>> py_enumerate_list_index_target()
+    [0] 1
+    [1] 2
+    [2] 3
+    [3] 4
+    """
+    target = [None]
+    for target[0],k in enumerate(range(1,5)):
+        print target, k
+
 @cython.test_fail_if_path_exists("//SimpleCallNode//NameNode[@name = 'enumerate']")
 def go_py_enumerate_start():
     """
@@ -39,6 +52,20 @@ def go_c_enumerate():
     for i,k in enumerate(range(1,5)):
         print i, k
 
+@cython.test_fail_if_path_exists("//SimpleCallNode//NameNode[@name = 'enumerate']")
+def c_enumerate_carray_target():
+    """
+    >>> c_enumerate_carray_target()
+    0 1
+    1 2
+    2 3
+    3 4
+    """
+    cdef int k
+    cdef int i[1]
+    for i[0],k in enumerate(range(1,5)):
+        print i[0], k
+
 @cython.test_fail_if_path_exists("//SimpleCallNode//NameNode[@name = 'enumerate']")
 def go_c_enumerate_step():
     """