Better scoring for loop breakers; fixes simplifier loop in nofib/minimax

[ghc-hetmet.git] / compiler / typecheck / TcType.lhs

diff --git a/compiler/typecheck/TcType.lhs b/compiler/typecheck/TcType.lhs
index 56351d7..3271ec2 100644 (file)
--- a/compiler/typecheck/TcType.lhs
+++ b/compiler/typecheck/TcType.lhs
@@ -45,7 +45,8 @@ module TcType (
   tcSplitFunTy_maybe, tcSplitFunTys, tcFunArgTy, tcFunResultTy, tcSplitFunTysN,
   tcSplitTyConApp, tcSplitTyConApp_maybe, tcTyConAppTyCon, tcTyConAppArgs,
   tcSplitAppTy_maybe, tcSplitAppTy, tcSplitAppTys, repSplitAppTy_maybe,
-  tcValidInstHeadTy, tcGetTyVar_maybe, tcGetTyVar,
+  tcInstHeadTyNotSynonym, tcInstHeadTyAppAllTyVars,
+  tcGetTyVar_maybe, tcGetTyVar,
   tcSplitSigmaTy, tcMultiSplitSigmaTy, 
 
   ---------------------------------
@@ -451,9 +452,9 @@ pprSkolTvBinding tv
 
     ppr_skol UnkSkol       = empty     -- Unhelpful; omit
     ppr_skol RuntimeUnkSkol = ptext SLIT("is an unknown runtime type")
-    ppr_skol info           = ptext SLIT("is a rigid type variable bound by") 
-                               <+> sep [pprSkolInfo info, 
-                                        nest 2 (ptext SLIT("at") <+> ppr (getSrcLoc tv))]
+    ppr_skol info           = sep [ptext SLIT("is a rigid type variable bound by"),
+                                  sep [pprSkolInfo info, 
+                                        nest 2 (ptext SLIT("at") <+> ppr (getSrcLoc tv))]]
  
 pprSkolInfo :: SkolemInfo -> SDoc
 pprSkolInfo (SigSkol ctxt)   = pprUserTypeCtxt ctxt
@@ -790,14 +791,23 @@ tcSplitDFunHead tau
        Just (ClassP clas tys) -> (clas, tys)
        other -> panic "tcSplitDFunHead"
 
-tcValidInstHeadTy :: Type -> Bool
+tcInstHeadTyNotSynonym :: Type -> Bool
 -- Used in Haskell-98 mode, for the argument types of an instance head
 -- These must not be type synonyms, but everywhere else type synonyms
 -- are transparent, so we need a special function here
-tcValidInstHeadTy ty
+tcInstHeadTyNotSynonym ty
   = case ty of
-       NoteTy _ ty     -> tcValidInstHeadTy ty
-       TyConApp tc tys -> not (isSynTyCon tc) && ok tys
+        NoteTy _ ty     -> tcInstHeadTyNotSynonym ty
+        TyConApp tc tys -> not (isSynTyCon tc)
+        _ -> True
+
+tcInstHeadTyAppAllTyVars :: Type -> Bool
+-- Used in Haskell-98 mode, for the argument types of an instance head
+-- These must be a constructor applied to type variable arguments
+tcInstHeadTyAppAllTyVars ty
+  = case ty of
+       NoteTy _ ty     -> tcInstHeadTyAppAllTyVars ty
+       TyConApp _ tys  -> ok tys
        FunTy arg res   -> ok [arg, res]
        other           -> False
   where
@@ -1153,13 +1163,11 @@ isFFIDotnetTy dflags ty
        --     it no longer does so.  May need to adjust isFFIDotNetTy
        --     if we do want to look through newtypes.
 
-isFFIDotnetObjTy ty = 
-  let
+isFFIDotnetObjTy ty
+  = checkRepTyCon check_tc t_ty
+  where
    (_, t_ty) = tcSplitForAllTys ty
-  in
-  case tcSplitTyConApp_maybe (repType t_ty) of
-    Just (tc, [arg_ty]) | getName tc == objectTyConName -> True
-    _ -> False
+   check_tc tc = getName tc == objectTyConName
 
 toDNType :: Type -> DNType
 toDNType ty
@@ -1242,7 +1250,11 @@ legalFFITyCon tc
   = isUnLiftedTyCon tc || boxedMarshalableTyCon tc || tc == unitTyCon
 
 marshalableTyCon dflags tc
-  =  (dopt Opt_GlasgowExts dflags && isUnLiftedTyCon tc)
+  =  (dopt Opt_UnliftedFFITypes dflags 
+      && isUnLiftedTyCon tc
+      && case tyConPrimRep tc of       -- Note [Marshalling VoidRep]
+          VoidRep -> False
+          other   -> True)
   || boxedMarshalableTyCon tc
 
 boxedMarshalableTyCon tc
@@ -1257,3 +1269,12 @@ boxedMarshalableTyCon tc
                         , boolTyConKey
                         ]
 \end{code}
+
+Note [Marshalling VoidRep]
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+We don't treat State# (whose PrimRep is VoidRep) as marshalable.
+In turn that means you can't write
+       foreign import foo :: Int -> State# RealWorld
+
+Reason: the back end falls over with panic "primRepHint:VoidRep";
+       and there is no compelling reason to permit it