Better location for broadcast check.

theano/scan_module/scan_op.py

@@ -402,7 +402,7 @@ class Scan(PureOp):
                     'by using dimshuffle or shape_padleft. '
                     )
 
-        def _check_broadcast(v1, v2):
+        def check_broadcast(v1, v2):
             """ Checks that the broadcast pattern of v1 and v2.
 
             Controls that the broadcast pattern of the variable provided as
@@ -444,7 +444,6 @@ class Scan(PureOp):
             rval = var
             if rval.type.dtype != as_var.type.dtype:
                 rval = rval.astype(as_var.type.dtype)
-            _check_broadcast(var, as_var)
             if rval.ndim == as_var.ndim:
                 rval = as_var.type.filter_variable(rval)
             else:
@@ -459,6 +458,7 @@ class Scan(PureOp):
         argoffset = 0
         for inner_seq, outer_seq in zip(self.inner_seqs(self.inputs),
                                         self.outer_seqs(inputs)):
+            check_broadcast(outer_seq, inner_seq)
             new_inputs.append(format(outer_seq, as_var=inner_seq))
 
         argoffset += len(self.outer_seqs(inputs))