add failing test case

tests/run/genexpr_iterable_lookup_T600.pyx

@@ -18,6 +18,7 @@ def list_genexpr_iterable_lookup():
     assert x == (0,1,2,3,4,5)
     return result
 
+
 #@cython.test_assert_path_exists('//ComprehensionNode')
 #@cython.test_fail_if_path_exists('//SingleAssignmentNode//SimpleCallNode')
 def genexpr_iterable_in_closure():
@@ -32,3 +33,11 @@ def genexpr_iterable_in_closure():
     assert x == 'abc' # don't leak in Py3 code
     assert f() == 'abc' # don't leak in Py3 code
     return result
+
+
+def genexpr_in_listcomp(L):
+    """
+    >>> genexpr_in_listcomp( [[1,2,3]]*2 )
+    [[1, 2, 3], [1, 2, 3]]
+    """
+    return [list(d for d in z) for z in L]