Checks the dimensions and bcast in inc_subtensor

theano/tensor/basic.py

@@ -4727,6 +4727,26 @@ def inc_subtensor(x, y, inplace=False, set_instead_of_inc=False,
 
     >>> new_r = inc_subtensor(r[10:], 5)
     """
+    # First of all, y cannot have a higher dimension than x,
+    # nor have non-broadcastable dimensions where x is broadcastable.
+    x = as_tensor_variable(x)
+    y = as_tensor_variable(y)
+    if y.ndim > x.ndim:
+        raise ValueError(("Trying to increment a %d-dimensional "
+            "subtensor with a %d-dimensional value.") % (x.ndim, y.ndim))
+
+    for dim in range(y.ndim):
+        dim_offset = x.ndim - y.ndim
+        if (x.broadcastable[dim + dim_offset]
+                and not y.broadcastable[dim]):
+            raise ValueError(("Trying to increment a subtensor with "
+                "broadcastable dimension %d, with a tensor not broadcastable "
+                "on corresponding dimension %d.") % (dim + dim_offset, dim),
+                x.broadcastable, y.broadcastable)
+
+    if not x.owner:
+        raise TypeError('x must be result of a subtensor operation')
+
     # retrieve idx_list from x.owner
     if isinstance(x.owner.op, Subtensor):
         if tolerate_inplace_aliasing:

theano/tensor/tests/test_inc_subtensor.py

@@ -56,6 +56,23 @@ class Test_inc_subtensor(unittest.TestCase):
 
             self.assertTrue(numpy.array_equal(result, expected_result))
 
+    def test_wrong_dims(self):
+        a = tt.matrix()
+        increment = tt.matrix()
+        index = 0
+
+        self.assertRaises(ValueError, tt.set_subtensor, a[index], increment)
+        self.assertRaises(ValueError, tt.inc_subtensor, a[index], increment)
+
+    def test_wrong_broadcast(self):
+        a = tt.col()
+        increment = tt.vector()
+
+        self.assertRaises(ValueError, tt.set_subtensor, a[:], increment)
+        self.assertRaises(ValueError, tt.set_subtensor, a[0], increment)
+        self.assertRaises(ValueError, tt.inc_subtensor, a[:], increment)
+        self.assertRaises(ValueError, tt.inc_subtensor, a[0], increment)
+
     def test_simple_3d(self):
         """Increments or sets part of a tensor by a scalar using full slice and
         a partial slice depending on a scalar.