diff --git a/parser-typechecker/src/Unison/Codecs.hs b/parser-typechecker/src/Unison/Codecs.hs
index 4546482c6..6fa9315b9 100644
--- a/parser-typechecker/src/Unison/Codecs.hs
+++ b/parser-typechecker/src/Unison/Codecs.hs
@@ -21,7 +21,7 @@ import qualified Unison.ABT as ABT
 import qualified Unison.Blank as Blank
 import qualified Unison.DataDeclaration as DD
 import qualified Unison.Hash as Hash
-import           Unison.Reference
+import           Unison.Reference (Reference(..))
 import           Unison.Term
 import qualified Unison.Typechecker.Components as Components
 import           Unison.UnisonFile (UnisonFile(..))
diff --git a/parser-typechecker/src/Unison/DataDeclaration.hs b/parser-typechecker/src/Unison/DataDeclaration.hs
index 5e44f6c79..33f7f6487 100644
--- a/parser-typechecker/src/Unison/DataDeclaration.hs
+++ b/parser-typechecker/src/Unison/DataDeclaration.hs
@@ -20,6 +20,7 @@ import qualified Unison.Reference as Reference
 import           Unison.Type (AnnotatedType)
 import qualified Unison.Type as Type
 import           Unison.Var (Var)
+import Unison.Hash (Hash)
 
 type DataDeclaration v = DataDeclaration' v ()
 
@@ -132,6 +133,15 @@ fromABT (ABT.AbsN' bound (
     [((), v, unsafeUnwrapType t) | (v, t) <- names `zip` stuff]
 fromABT a = error $ "ABT not of correct form to convert to DataDeclaration: " ++ show a
 
+hashDecls2
+  :: (Eq v, Var v)
+  => Map v (DataDeclaration' v a)
+  -> [(Hash, [v])]
+hashDecls2 decls = fixup <$> ABT.hashComponents mkRef (toABT . void <$> decls)
+  where mkRef h i = ABT.tm (Type (Type.Ref (Reference.Derived h)))
+        fixup (h, scc) = (h, fst <$> scc)
+-- use this to impl hashDecls
+
 -- Implementation detail of `hashDecls`, works with unannotated data decls
 hashDecls0
   :: (Eq v, Var v)
diff --git a/parser-typechecker/src/Unison/Reference.hs b/parser-typechecker/src/Unison/Reference.hs
index 9f70156b9..40efedd50 100644
--- a/parser-typechecker/src/Unison/Reference.hs
+++ b/parser-typechecker/src/Unison/Reference.hs
@@ -6,11 +6,26 @@ import GHC.Generics
 import Unison.Hashable as Hashable
 import qualified Data.Text as Text
 import qualified Unison.Hash as H
+import Data.Word (Word64)
 
 -- could add a `Word` parameter to `Derived`
 -- associated with each hash would actually be a list of terms / type decls
 data Reference = Builtin Text.Text | Derived H.Hash deriving (Eq,Ord,Generic)
 
+type Pos = Word64
+type Size = Word64
+
+derived :: H.Hash -> Pos -> Size -> Reference
+derived _h _pos _size = error "todo"
+
+component :: H.Hash -> [k] -> [(k, Reference)]
+component h ks = let
+  size = fromIntegral (length ks)
+  in [ (k, derived h i size) | (k, i) <- ks `zip` [0..]]
+
+components :: [(H.Hash, [k])] -> [[(k, Reference)]]
+components sccs = uncurry component <$> sccs
+
 instance Show Reference where
   show (Builtin t) = Text.unpack t
   show (Derived h) = "#" <> show h