Fix a case in local_subtensor_lift where the optimization was failing.

theano/tensor/opt.py

@@ -1105,7 +1105,7 @@ def local_subtensor_lift(node):
                         if node.outputs[0].ndim == i.ndim:
                             new_inputs.append(i)
                         else:
-                            new_inputs.append(i.dimshuffle('x'*node.outputs[0].ndim))
+                            new_inputs.append(i.dimshuffle(['x']*node.outputs[0].ndim))
                 return [u.owner.op(*new_inputs)]
 
 @register_canonicalize

theano/tensor/tests/test_opt.py

@@ -1244,6 +1244,22 @@ class test_local_subtensor_lift(unittest.TestCase):
         assert len(prog)==4
         f([[0,1],[2,3]], [4,5]) # let debugmode test something
 
+    def test6(self):
+        # basic test that the optimization works with a scalar as input,
+        # and a scalar as output (no broadcasting of the scalar needed).
+        # The optimization used to fail and display an ERROR message.
+
+        x = TT.vector('x')
+        y = TT.scalar('y')
+        f = function([x,y], TT.exp(x+y)[0], mode=mode_opt)
+
+        prog=f.maker.env.toposort()
+        assert isinstance(prog[0].op, TT.Subtensor)
+        # Composite{add,exp}
+        assert isinstance(prog[1].op.scalar_op, theano.scalar.Composite)
+        assert len(prog)==2
+        f([1,2,3], 4) # let debugmode test something
+
 class test_local_subtensor_merge(unittest.TestCase):
 
     def test_const(self):