Fix and improve deriving for indexed data types

[ghc-hetmet.git] / compiler / types / Type.lhs

diff --git a/compiler/types/Type.lhs b/compiler/types/Type.lhs
index d81278a..147f546 100644 (file)
--- a/compiler/types/Type.lhs
+++ b/compiler/types/Type.lhs
@@ -55,7 +55,7 @@ module Type (
 
        -- Source types
        predTypeRep, mkPredTy, mkPredTys,
-       tyConOrigHead,
+       tyConOrigHead, pprSourceTyCon,
 
        -- Newtypes
        splitRecNewType_maybe, newTyConInstRhs,
@@ -609,6 +609,13 @@ tyConOrigHead :: TyCon -> (TyCon, [Type])
 tyConOrigHead tycon = case tyConFamInst_maybe tycon of
                        Nothing      -> (tycon, mkTyVarTys (tyConTyVars tycon))
                        Just famInst -> famInst
+
+-- Pretty prints a tycon, using the family instance in case of a
+-- representation tycon.
+pprSourceTyCon tycon | Just (repTyCon, tys) <- tyConFamInst_maybe tycon =
+  ppr $ repTyCon `TyConApp` tys               -- can't be FunTyCon
+                     | otherwise                                        =
+  ppr tycon
 \end{code}