Fix crash tensor.roll(Var, iscalar) reported by Jeremiah Lowin.

theano/tensor/basic.py

@@ -5632,8 +5632,8 @@ def roll(x, shift, axis=None):
     end_list = ([allslice] * axis + [end_slice] +
                 [allslice] * (x.ndim - axis - 1))
     return join(axis,
-                Subtensor(front_list)(x),
-                Subtensor(end_list)(x))
+                x.__getitem__(tuple(front_list)),
+                x.__getitem__(tuple(end_list)))
 
 
 @constructor

theano/tensor/tests/test_basic.py

@@ -3625,16 +3625,17 @@ class T_Join_and_Split(unittest.TestCase):
 
     def test_roll(self):
 
+        for get_shift in [lambda a:a, lambda x:theano.shared(x)]:
             # Test simple 1D example
             a = self.shared(numpy.array([1, 2, 3, 4, 5, 6], dtype=self.floatX))
-        b = roll(a, 2)
+            b = roll(a, get_shift(2))
             want = numpy.array([5, 6, 1, 2, 3, 4])
             out = theano.function([], b)()
 
             assert (out == want).all()
 
             # Test simple 1D example with explicit 0 axis
-        b = roll(a, -1, 0)
+            b = roll(a, get_shift(-1), 0)
             want = numpy.array([2, 3, 4, 5, 6, 1])
             out = theano.function([], b)()
 
@@ -3642,7 +3643,7 @@ class T_Join_and_Split(unittest.TestCase):
 
             # Test 2D example - ensure that behavior matches numpy.roll behavior
             a = self.shared(numpy.arange(21).reshape((3, 7)).astype(self.floatX))
-        b = roll(a, -2, 1)
+            b = roll(a, get_shift(-2), 1)
 
             want = numpy.roll(a.get_value(borrow=True), -2, 1)
             out = theano.function([], b)()
@@ -3651,14 +3652,14 @@ class T_Join_and_Split(unittest.TestCase):
 
             # Test rolling on axis 0
             want = numpy.roll(a.get_value(borrow=True), -2, 0)
-        b = roll(a, -2, 0)
+            b = roll(a, get_shift(-2), 0)
             out = theano.function([], b)()
 
             assert (out == want).all()
 
             # Test rolling on default axis with ndim > 1
             want = numpy.roll(a.get_value(borrow=True), 2)
-        b = roll(a, 2)
+            b = roll(a, get_shift(2))
             out = theano.function([], b)()
 
             assert (out == want).all()