diff --git a/pass/Pass.hs b/pass/Pass.hs
index d3b93fb..1cebbda 100644
--- a/pass/Pass.hs
+++ b/pass/Pass.hs
@@ -59,6 +59,12 @@ type PassType t = t -> PassM t
 type PassOnOps ops
   = (PolyplateM t ops () PassM, PolyplateM t () ops PassM) => Pass t
 
+type CheckOnOps ops
+  = (PolyplateSpine t ops () (PassM ())) => Pass t
+
+type PlainCheckOnOps ops
+  = (PolyplateSpine t ops () (PassM ())) => t -> PassM ()
+
 type PassASTOnOps ops
   = (PolyplateM A.AST ops () PassM, PolyplateM A.AST () ops PassM) => Pass A.AST
 
@@ -68,7 +74,8 @@ type PassTypeOnOps ops
 type PassOn t = PassOnOps (OneOpM PassM t)
 type PassOn2 s t = PassOnOps (TwoOpM PassM s t)
 type PassTypeOn t = PassTypeOnOps (OneOpM PassM t)
-      
+type CheckOn t = CheckOnOps (OneOpQ (PassM ()) t)
+type PlainCheckOn t = PlainCheckOnOps (OneOpQ (PassM ()) t)
 
 -- | A description of an AST-mangling pass.
 data Pass t = Pass {
diff --git a/pass/Traversal.hs b/pass/Traversal.hs
index 4aaa855..9d58b3c 100644
--- a/pass/Traversal.hs
+++ b/pass/Traversal.hs
@@ -21,7 +21,7 @@ with this program.  If not, see <http://www.gnu.org/licenses/>.
 module Traversal (
     TransformM, Transform, TransformStructured
   , CheckM, Check
-  , ExtOpMP, ExtOpMS, ExtOpMSP, extOpMS
+  , ExtOpMP, ExtOpMS, ExtOpMSP, extOpMS, PassOnStruct
   , applyBottomUpMS
   , module Data.Generics.Polyplate
   , module Data.Generics.Polyplate.Schemes
@@ -35,7 +35,8 @@ import Data.Generics.Polyplate.Schemes
 
 import qualified AST as A
 import GenericUtils
-import NavAST
+import NavAST()
+import NavASTSpine()
 import Pass
 
 -- | A transformation for a single 'Data' type.
@@ -65,6 +66,8 @@ type ExtOpMS m opT =
           opT)))))))
 type ExtOpMSP opT = ExtOpMS PassM opT
 
+type PassOnStruct = PassOnOps (ExtOpMSP BaseOp)
+
 extOpMS :: forall m opT op0T.
           (PolyplateM (A.Structured ()) () op0T m,
            PolyplateM (A.Structured A.Alternative) () op0T m,