fix for outputGuard

theano/compile/function_module.py

@@ -136,7 +136,6 @@ class Supervisor:
             if fgraph.has_destroyers(self.protected):
                 raise gof.InconsistencyError("Trying to destroy a protected"
                                              "Variable.")
-            else:
             return True
         if not hasattr(fgraph, 'destroyers'):
             return True

theano/gof/destroyhandler.py

@@ -398,6 +398,7 @@ class DestroyHandler(toolbox.Bookkeeper):  # noqa
             visited_app_set = set()
 
             def recursive_destroys_finder(protected_var):
+                # protected_var is the idx'th input of app.
                 for (app, idx) in protected_var.clients:
                     if app in visited_app_set:
                         continue
@@ -406,16 +407,21 @@ class DestroyHandler(toolbox.Bookkeeper):  # noqa
                     if app == 'output':
                         continue
                     destroy_maps = getattr(app.op, 'destroy_map', {}).values()
+                    # If True means that the apply node, destroys the protected_var.
                     if idx in [dmap for sublist in destroy_maps for dmap in sublist]:
                         return True
                     for var_idx in getattr(app.op, 'view_map', {}).keys():
-                        if idx in app.op.view_map[var_idx] and recursive_destroys_finder(app.outputs[var_idx]):
+                        if idx in app.op.view_map[var_idx]:
+                            # We need to recursivly check the destroy_map of all the
+                            # outputs that we have a view_map on.
+                            if recursive_destroys_finder(app.outputs[var_idx]):
                                 return True
                 return False
 
             for protected_var in protected_list:
                 if recursive_destroys_finder(protected_var):
                     return True
+            return False
 
         fgraph.has_destroyers = has_destroyers
 
@@ -445,7 +451,7 @@ class DestroyHandler(toolbox.Bookkeeper):  # noqa
         delattr(self.fgraph, 'destroy_handler')
         self.fgraph = None
 
-    def fast_destroy(self, app, reason):
+    def fast_destroy(self, app, reason, full=False):
         """
         Do the check for only 1 level.
 
@@ -456,6 +462,7 @@ class DestroyHandler(toolbox.Bookkeeper):  # noqa
         - But don't allow to destroy view
         """
         dm = getattr(app.op, 'destroy_map', None)
+        vm = getattr(app.op, 'view_map', {})
         if not dm:
             return
         inputs = set(itertools.chain.from_iterable(dm.values()))   # list of app's destroyed inputs
@@ -489,6 +496,17 @@ class DestroyHandler(toolbox.Bookkeeper):  # noqa
                 # assert len(v) <= 1
                 # assert len(d) <= 1
 
+        # We don't want this to be a regular check. Full is only enabled when a node is
+        # attached to the graph and at the end of validation. We check a rare case where
+        # an apply node has a dmap and vmap on the same input. Right now the only case
+        # of this pattern is when app is the OutputGuard.
+        if full:
+            d_inputs = set(dmap for sublist in dm.values() for dmap in sublist)
+            v_inputs = set(vmap for sublist in vm.values() for vmap in sublist)
+            if d_inputs.intersection(v_inputs):
+                self.fail_validate[app] = theano.gof.InconsistencyError("\
+                    Destroyed variable has both view_map and destroy_map. " + str(reason))
+
     def on_import(self, fgraph, app, reason):
         """
         Add Apply instance to set which must be computed.
@@ -500,13 +518,15 @@ class DestroyHandler(toolbox.Bookkeeper):  # noqa
         # print 'DH IMPORT', app, id(app), id(self), len(self.debug_all_apps)
 
         # If it's a destructive op, add it to our watch list
-        if getattr(app.op, 'destroy_map', None):
+        dmap = getattr(app.op, 'destroy_map', None)
+        vmap = getattr(app.op, 'view_map', {})
+        if dmap:
             self.destroyers.add(app)
             if self.algo == 'fast':
-                self.fast_destroy(app, reason)
+                self.fast_destroy(app, reason, full=True)
 
         # add this symbol to the forward and backward maps
-        for o_idx, i_idx_list in iteritems(getattr(app.op, 'view_map', {})):
+        for o_idx, i_idx_list in iteritems(vmap):
             if len(i_idx_list) > 1:
                 raise NotImplementedError(
                     'destroying this output invalidates multiple inputs',
@@ -635,7 +655,7 @@ class DestroyHandler(toolbox.Bookkeeper):  # noqa
                     # double check here.
                     for app in app_err_pairs:
                         if app in fgraph.apply_nodes:
-                            self.fast_destroy(app, 'validate')
+                            self.fast_destroy(app, 'validate', full=True)
                     if self.fail_validate:
                         self.fail_validate = app_err_pairs
                         raise app_err_pairs[app]