Improve handling of newtypes (fixes Trac 1495)

[ghc-hetmet.git] / compiler / iface / BuildTyCl.lhs

diff --git a/compiler/iface/BuildTyCl.lhs b/compiler/iface/BuildTyCl.lhs
index 80428a7..534bc5f 100644 (file)
--- a/compiler/iface/BuildTyCl.lhs
+++ b/compiler/iface/BuildTyCl.lhs
@@ -146,10 +146,9 @@ mkNewTyConRhs tycon_name tycon con
        ; return (NewTyCon { data_con    = con, 
                             nt_rhs      = rhs_ty,
                             nt_etad_rhs = (etad_tvs, etad_rhs),
-                            nt_co       = cocon_maybe, 
+                            nt_co       = cocon_maybe } ) }
                              -- Coreview looks through newtypes with a Nothing
                              -- for nt_co, or uses explicit coercions otherwise
-                            nt_rep = mkNewTyConRep tycon rhs_ty }) }
   where
         -- If all_coercions is True then we use coercions for all newtypes
         -- otherwise we use coercions for recursive newtypes and look through
@@ -180,42 +179,6 @@ mkNewTyConRhs tycon_name tycon con
     eta_reduce tvs ty = (reverse tvs, ty)
                                
 
-mkNewTyConRep :: TyCon         -- The original type constructor
-             -> Type           -- The arg type of its constructor
-             -> Type           -- Chosen representation type
--- The "representation type" is guaranteed not to be another newtype
--- at the outermost level; but it might have newtypes in type arguments
-
--- Find the representation type for this newtype TyCon
--- Remember that the representation type is the *ultimate* representation
--- type, looking through other newtypes.
--- 
--- splitTyConApp_maybe no longer looks through newtypes, so we must
--- deal explicitly with this case
--- 
--- The trick is to to deal correctly with recursive newtypes
--- such as     newtype T = MkT T
-
-mkNewTyConRep tc rhs_ty
-  | null (tyConDataCons tc) = unitTy
-       -- External Core programs can have newtypes with no data constructors
-  | otherwise              = go [tc] rhs_ty
-  where
-       -- Invariant: tcs have been seen before
-    go tcs rep_ty 
-       = case splitTyConApp_maybe rep_ty of
-           Just (tc, tys)
-               | tc `elem` tcs -> unitTy       -- Recursive loop
-               | isNewTyCon tc -> 
-                    if isRecursiveTyCon tc then
-                       go (tc:tcs) (substTyWith tvs tys rhs_ty)
-                    else
-                        substTyWith tvs tys rhs_ty
-               where
-                 (tvs, rhs_ty) = newTyConRhs tc
-
-           other -> rep_ty 
-
 ------------------------------------------------------
 buildDataCon :: Name -> Bool
            -> [StrictnessMark]