Bug/crash fix. crash fix reported, but it is not sure it would always return a crash.

theano/tensor/opt_uncanonicalize.py

@@ -217,7 +217,7 @@ def local_dimshuffle_subtensor(node):
             j = 0
             slice_i = -1
             subtensor_removed_dims = 0
-            for idx in input_.owner.op.idx_list:
+            for i, idx in enumerate(input_.owner.op.idx_list):
                 if isinstance(idx, slice):
                     past_j = j
                     slice_i += 1
@@ -229,7 +229,7 @@ def local_dimshuffle_subtensor(node):
                     # that's where we want to index with 0 if it is also at
                     # the same spot of a missing dim
                     if past_j == j and slice_i in missing_dims:
-                        new_idx_list[j] = zero
+                        new_idx_list[i] = zero
                         new_inputs += [zero]
                 else:
                     new_inputs += [input_.owner.inputs[1 + j]]

theano/tensor/tests/test_opt_uncanonicalize.py

@@ -207,3 +207,9 @@ def test_local_dimshuffle_subtensor():
     topo = f.maker.fgraph.toposort()
     assert any([not isinstance(x, DimShuffle) for x in topo])
     assert f(np.random.rand(5, 1, 4, 1), 2).shape == (4,)
+
+    # Test a corner case that had Theano return a bug.
+    x = tensor.dtensor4('x')
+    x = tensor.patternbroadcast(x, (False, True, False, False))
+
+    assert x[:,:, 0:3, ::-1].dimshuffle(0,2,3).eval({x: np.ones((5, 1, 6, 7))}).shape == (5, 3, 7)