Clearer error message

theano/scan_module/scan_op.py

@@ -205,13 +205,18 @@ class Scan(PureOp):
                    )
         err_msg2 = ('When compiling the inner function of scan the '
                     'following error has been encountered: The '
-                    'initial state (outputs_info in scan nomenclature) '
-                    'of variable %s (argument number %d)'
-                    ' has dtype %s and %d dimension(s), while the result '
-                    'of the inner function for this output has dtype %s '
-                    'and %d dimension(s). This could happen if the inner '
-                    'graph of scan results in an upcast or downcast. '
-                    'Please make sure that you use dtypes consistently')
+                    'initial state (`outputs_info` in scan nomenclature) '
+                    'of variable %s (argument number %d) '
+                    'has dtype %s, while the result of the inner function '
+                    '(`fn`) has dtype %s. This can happen if the inner '
+                    'function of scan results in an upcast or downcast.')
+        err_msg3 = ('When compiling the inner function of scan the '
+                    'following error has been encountered: The '
+                    'initial state (`outputs_info` in scan nomenclature) '
+                    'of variable %s (argument number %d) has %d dimension(s), '
+                    'while the result of the inner function (`fn`) has %d '
+                    'dimension(s) (should be one less than the initial '
+                    'state).')
 
         def format(var, as_var):
             """ This functions ensures that ``out`` has the same dtype as
@@ -272,17 +277,19 @@ class Scan(PureOp):
                                            inner_mitmot[ipos + k].type.ndim))
             ipos += len(itaps)
             for k in xrange(len(otaps)):
-                if (inner_mitmot_outs[opos + k].type.dtype != \
-                        outer_mitmot.type.dtype or
-                    inner_mitmot_outs[opos + k].ndim != \
-                         outer_mitmot.ndim - 1):
+                if (inner_mitmot_outs[opos + k].type.dtype !=
+                        outer_mitmot.type.dtype):
                     raise ValueError(err_msg2 %
-                                      (str(outer_mitmot),
-                                       argoffset + idx,
-                                       outer_mitmot.type.dtype,
-                                       outer_mitmot.ndim - 1,
-                                       inner_mitmot_outs[opos + k].type.dtype,
-                                       inner_mitmot_outs[opos + k].ndim))
+                                     (str(outer_mitmot),
+                                      argoffset + idx,
+                                      outer_mitmot.type.dtype,
+                                      inner_mitmot_outs[opos + k].type.dtype))
+                if inner_mitmot_outs[opos + k].ndim != outer_mitmot.ndim - 1:
+                    raise ValueError(err_msg3 %
+                                     (str(outer_mitmot),
+                                      argoffset + idx,
+                                      outer_mitmot.ndim,
+                                      inner_mitmot_outs[opos + k].ndim))
             opos += len(otaps)
         argoffset += len(self.outer_mitmot(inputs))
         # Same checks as above but for outputs of type mit_sot
@@ -309,15 +316,18 @@ class Scan(PureOp):
                                            inner_mitsots[ipos + k].type.dtype,
                                            inner_mitsots[ipos + k].type.ndim))
             ipos += len(itaps)
-            if (inner_mitsot_out.type.dtype != outer_mitsot.type.dtype or
-                inner_mitsot_out.ndim != outer_mitsot.ndim - 1):
+            if inner_mitsot_out.type.dtype != outer_mitsot.type.dtype:
                 raise ValueError(err_msg2 %
                                  (str(outer_mitsot),
-                                 argoffset + idx,
-                                 outer_mitsot.type.dtype,
-                                 outer_mitsot.type.ndim,
-                                 inner_mitsot_out.type.dtype,
-                                 inner_mitsot_out.type.ndim))
+                                  argoffset + idx,
+                                  outer_mitsot.type.dtype,
+                                  inner_mitsot_out.type.dtype))
+            if inner_mitsot_out.ndim != outer_mitsot.ndim - 1:
+                raise ValueError(err_msg3 %
+                                 (str(outer_mitsot),
+                                  argoffset + idx,
+                                  outer_mitsot.ndim,
+                                  inner_mitsot_out.ndim))
 
         argoffset += len(self.outer_mitsot(inputs))
         # Same checks as above but for outputs of type sit_sot
@@ -337,15 +347,18 @@ class Scan(PureOp):
                                 str(inner_sitsot),
                                 inner_sitsot.type.dtype,
                                 inner_sitsot.type.ndim))
-            if (inner_sitsot_out.type.dtype != outer_sitsot.type.dtype or
-                inner_sitsot_out.ndim != outer_sitsot.ndim - 1):
+            if inner_sitsot_out.type.dtype != outer_sitsot.type.dtype:
                 raise ValueError(err_msg2 %
-                                (str(outer_sitsot),
-                                argoffset + idx,
-                                outer_sitsot.type.dtype,
-                                outer_sitsot.type.ndim,
-                                inner_sitsot_out.type.dtype,
-                                inner_sitsot_out.type.ndim))
+                                 (str(outer_sitsot),
+                                  argoffset + idx,
+                                  outer_sitsot.type.dtype,
+                                  inner_sitsot_out.type.dtype))
+            if inner_sitsot_out.ndim != outer_sitsot.ndim - 1:
+                raise ValueError(err_msg3 %
+                                 (str(outer_sitsot),
+                                  argoffset + idx,
+                                  outer_sitsot.type.ndim,
+                                  inner_sitsot_out.type.ndim))
 
         argoffset += len(self.outer_sitsot(inputs))
         # Check that the shared variable and their update rule have the same
@@ -357,13 +370,16 @@ class Scan(PureOp):
             outer_shared = format(_outer_shared, as_var=inner_shared)
             new_inputs.append(outer_shared)
             if (hasattr(outer_shared, 'dtype') and
-                (outer_shared.dtype != inner_shared_out.dtype or
-                 outer_shared.ndim != inner_shared_out.ndim)):
+                    outer_shared.dtype != inner_shared_out.dtype):
                 raise ValueError(err_msg2 % (str(outer_shared),
                                              idx + argoffset,
                                              outer_shared.dtype,
+                                             inner_shared_out.dtype))
+            if (hasattr(outer_shared, 'dtype') and
+                    outer_shared.ndim != inner_shared_out.ndim):
+                raise ValueError(err_msg3 % (str(outer_shared),
+                                             idx + argoffset,
                                              outer_shared.ndim,
-                                             inner_shared_out.dtype,
                                              inner_shared_out.ndim))
 
             if (hasattr(outer_shared, 'dtype') and