Update and move Feature accoding to feedback

theano/gof/__init__.py

@@ -46,7 +46,7 @@ from theano.gof.fg import \
     CachedConstantError, InconsistencyError, MissingInputError, FunctionGraph
 
 from theano.gof.destroyhandler import \
-    DestroyHandler, NoOutputFromInplace
+    DestroyHandler
 
 from theano.gof.graph import \
     Apply, Variable, Constant, view_roots
@@ -74,7 +74,7 @@ from theano.gof.optdb import \
 from theano.gof.toolbox import \
     Feature, \
     Bookkeeper, History, Validator, ReplaceValidate, NodeFinder,\
-    PrintListener, ReplacementDidntRemovedError
+    PrintListener, ReplacementDidntRemovedError, NoOutputFromInplace
 
 from theano.gof.type import \
     Type, Generic, generic

theano/gof/destroyhandler.py

@@ -7,7 +7,6 @@ import toolbox
 import graph
 from theano.gof.python25 import deque
 from theano.gof.python25 import OrderedDict
-from theano.gof.toolbox import Feature
 from theano.misc.ordered_set import OrderedSet
 
 from fg import InconsistencyError
@@ -1027,23 +1026,3 @@ class DestroyHandler(toolbox.Bookkeeper):
                         rval[app] = root_clients
 
         return rval
-
-
-class NoOutputFromInplace(Feature):
-
-    def __init__(self):
-        pass
-
-    def validate(self, fgraph):
-        if not hasattr(fgraph, 'destroyers'):
-            return True
-        for out in list(fgraph.outputs):
-            # Validate that the node that produces the output does not produce
-            # it by modifying something else inplace.
-            node = out.owner
-            op = node.op
-            out_idx = node.outputs.index(out)
-            if hasattr(op, 'destroy_map') and out_idx in op.destroy_map.keys():
-                raise InconsistencyError(
-                    "Trying to produce an output ", out,
-                     " by modifying another variable inplace")

theano/gof/toolbox.py

 import sys
 import time
 
+import theano
 from theano import config
 from theano.gof.python25 import partial
 from theano.gof.python25 import OrderedDict
@@ -394,3 +395,26 @@ class PreserveNames(Feature):
             new_r.name = r.name
 
 
+class NoOutputFromInplace(Feature):
+
+    def validate(self, fgraph):
+        if not hasattr(fgraph, 'destroyers'):
+            return True
+        for out in list(fgraph.outputs):
+
+            if out.owner is None:
+                continue
+
+            # Validate that the node that produces the output does not produce
+            # it by modifying something else inplace.
+            node = out.owner
+            op = node.op
+            out_idx = node.outputs.index(out)
+            if hasattr(op, 'destroy_map') and out_idx in op.destroy_map.keys():
+                raise theano.gof.InconsistencyError(
+                    "A function graph Feature has requested (probably for ",
+                    "efficiency reasons for scan) that outputs of the graph",
+                    "be prevented from being the result of inplace ",
+                    "operations. This has prevented output ", out, " from ",
+                    "being the computed by modifying another variable ",
+                    "inplace.")