Raising error for Indexing subtensor with a Boolean mask

theano/tensor/tests/test_subtensor.py

@@ -383,7 +383,7 @@ class T_subtensor(unittest.TestCase, utt.TestOptimizationMixin):
         subi = 0
         data = numpy.asarray(rand(2, 3), dtype=self.dtype)
         n = self.shared(data)
-        z = scal.constant(subi)
+        z = scal.constant(subi).astype('int32')
         t = n[z:, z]
         gn = theano.tensor.grad(theano.tensor.sum(theano.tensor.exp(t)), n)
 

theano/tensor/var.py

 from __future__ import absolute_import, print_function, division
+import collections
 import copy
 import traceback as tb
 import warnings
@@ -466,6 +467,25 @@ class _tensor_py_operators(object):
 
     # SLICING/INDEXING
     def __getitem__(self, args):
+
+        def check_bool(args_el):
+            try:
+                if isinstance(args_el, (numpy.bool_, bool)) or \
+                   args_el.dtype == 'int8' or args_el.dtype == 'uint8':
+                    raise TypeError(('TensorType does not support boolean '
+                                     'mask for indexing such as tensor[x==0]. '
+                                     'If you are indexing on purpose with an '
+                                     'int8, please cast it to int32'))
+            except AttributeError:
+                pass
+
+            if not isinstance(args_el, theano.tensor.Variable) and \
+               isinstance(args_el, collections.Iterable):
+                for el in args_el:
+                    check_bool(el)
+
+        check_bool(args)
+
         if (isinstance(args, list) and
                 any([isinstance(a, slice) for a in args])):
             pass