fix bugs, add boolean flag to identify coercion variables

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

diff --git a/compiler/iface/BuildTyCl.lhs b/compiler/iface/BuildTyCl.lhs
index 5c76d55..d1118c0 100644 (file)
--- a/compiler/iface/BuildTyCl.lhs
+++ b/compiler/iface/BuildTyCl.lhs
@@ -29,7 +29,7 @@ import Class          ( mkClass, Class( classTyCon), FunDep, DefMeth(..) )
 import TyCon           ( mkSynTyCon, mkAlgTyCon, visibleDataCons, tyConStupidTheta,
                          tyConDataCons, isNewTyCon, mkClassTyCon, TyCon( tyConTyVars ),
                          isRecursiveTyCon, tyConArity,
-                         ArgVrcs, AlgTyConRhs(..), newTyConRhs )
+                         AlgTyConRhs(..), newTyConRhs )
 import Type            ( mkArrowKinds, liftedTypeKind, typeKind, 
                          tyVarsOfType, tyVarsOfTypes, tyVarsOfPred,
                          splitTyConApp_maybe, splitAppTy_maybe, getTyVar_maybe,
@@ -45,8 +45,8 @@ import List           ( nub )
 
 \begin{code}
 ------------------------------------------------------
-buildSynTyCon name tvs rhs_ty arg_vrcs
-  = mkSynTyCon name kind tvs rhs_ty arg_vrcs
+buildSynTyCon name tvs rhs_ty
+  = mkSynTyCon name kind tvs rhs_ty
   where
     kind = mkArrowKinds (map tyVarKind tvs) (typeKind rhs_ty)
 
@@ -55,13 +55,13 @@ buildSynTyCon name tvs rhs_ty arg_vrcs
 buildAlgTyCon :: Name -> [TyVar] 
              -> ThetaType              -- Stupid theta
              -> AlgTyConRhs
-             -> ArgVrcs -> RecFlag
+             -> RecFlag
              -> Bool                   -- True <=> want generics functions
              -> Bool                   -- True <=> was declared in GADT syntax
              -> TcRnIf m n TyCon
 
-buildAlgTyCon tc_name tvs stupid_theta rhs arg_vrcs is_rec want_generics gadt_syn
-  = do { let { tycon = mkAlgTyCon tc_name kind tvs arg_vrcs stupid_theta
+buildAlgTyCon tc_name tvs stupid_theta rhs is_rec want_generics gadt_syn
+  = do { let { tycon = mkAlgTyCon tc_name kind tvs stupid_theta
                                   rhs fields is_rec want_generics gadt_syn
              ; kind    = mkArrowKinds (map tyVarKind tvs) liftedTypeKind
              ; fields  = mkTyConSelIds tycon rhs
@@ -82,13 +82,24 @@ mkNewTyConRhs :: Name -> TyCon -> DataCon -> TcRnIf m n AlgTyConRhs
 -- because the latter is part of a knot, whereas the former is not.
 mkNewTyConRhs tycon_name tycon con 
   = do { co_tycon_name <- newImplicitBinder tycon_name mkNewTyCoOcc
-       ; let co_tycon = mkNewTypeCoercion co_tycon_name tycon tvs rhs_ty 
+       ; let co_tycon = mkNewTypeCoercion co_tycon_name tycon tvs rhs_ty
+              cocon_maybe 
+                | all_coercions || isRecursiveTyCon tycon 
+                = Just co_tycon
+                | otherwise              
+                = Nothing
        ; return (NewTyCon { data_con = con, 
-                            nt_co = co_tycon,
+                            nt_co = cocon_maybe, 
+                             -- Coreview looks through newtypes with a Nothing
+                             -- for nt_co, or uses explicit coercions otherwise
                             nt_rhs = rhs_ty,
                             nt_etad_rhs = eta_reduce tvs rhs_ty,
                             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
+        -- non-recursive newtypes
+    all_coercions = True
     tvs    = tyConTyVars tycon
     rhs_ty = head (dataConInstOrigArgTys con (mkTyVarTys tvs))
        -- Instantiate the data con with the 
@@ -116,9 +127,8 @@ mkNewTyConRep :: TyCon              -- The original type constructor
 -- Remember that the representation type is the *ultimate* representation
 -- type, looking through other newtypes.
 -- 
--- The non-recursive newtypes are easy, because they look transparent
--- to splitTyConApp_maybe, but recursive ones really are represented as
--- TyConApps (see TypeRep).
+-- 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
@@ -133,10 +143,11 @@ mkNewTyConRep tc rhs_ty
        = case splitTyConApp_maybe rep_ty of
            Just (tc, tys)
                | tc `elem` tcs -> unitTy       -- Recursive loop
-               | isNewTyCon tc -> ASSERT( isRecursiveTyCon tc )
-                                       -- Non-recursive ones have been 
-                                       -- dealt with by splitTyConApp_maybe
-                                  go (tc:tcs) (substTyWith tvs tys rhs_ty)
+               | 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
 
@@ -207,10 +218,10 @@ mkTyConSelIds tycon rhs
 buildClass :: Name -> [TyVar] -> ThetaType
           -> [FunDep TyVar]            -- Functional dependencies
           -> [(Name, DefMeth, Type)]   -- Method info
-          -> RecFlag -> ArgVrcs        -- Info for type constructor
+          -> RecFlag                   -- Info for type constructor
           -> TcRnIf m n Class
 
-buildClass class_name tvs sc_theta fds sig_stuff tc_isrec tc_vrcs
+buildClass class_name tvs sc_theta fds sig_stuff tc_isrec
   = do { tycon_name <- newImplicitBinder class_name mkClassTyConOcc
        ; datacon_name <- newImplicitBinder class_name mkClassDataConOcc
                -- The class name is the 'parent' for this datacon, not its tycon,
@@ -253,7 +264,7 @@ buildClass class_name tvs sc_theta fds sig_stuff tc_isrec tc_vrcs
        ; let { clas_kind = mkArrowKinds (map tyVarKind tvs) liftedTypeKind
 
              ; tycon = mkClassTyCon tycon_name clas_kind tvs
-                             tc_vrcs rhs rec_clas tc_isrec
+                             rhs rec_clas tc_isrec
                -- A class can be recursive, and in the case of newtypes 
                -- this matters.  For example
                --      class C a where { op :: C b => a -> b -> Int }