Float out partial applications

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

diff --git a/compiler/typecheck/TcMType.lhs b/compiler/typecheck/TcMType.lhs
index a3484a9..b31a4cc 100644 (file)
--- a/compiler/typecheck/TcMType.lhs
+++ b/compiler/typecheck/TcMType.lhs
@@ -57,6 +57,7 @@ module TcMType (
   zonkTcType, zonkTcTypes, zonkTcThetaType,
   zonkTcKindToKind, zonkTcKind, 
   zonkImplication, zonkWanted, zonkEvVar, zonkWantedEvVar,
+  zonkTcTypeAndSubst,
   tcGetGlobalTyVars, 
 
   readKindVar, writeKindVar
@@ -468,7 +469,7 @@ tcGetGlobalTyVars :: TcM TcTyVarSet
 tcGetGlobalTyVars
   = do { (TcLclEnv {tcl_tyvars = gtv_var}) <- getLclEnv
        ; gbl_tvs  <- readMutVar gtv_var
-       ; gbl_tvs' <- zonkTcTyVarsAndFV (varSetElems gbl_tvs)
+       ; gbl_tvs' <- zonkTcTyVarsAndFV gbl_tvs
        ; writeMutVar gtv_var gbl_tvs'
        ; return gbl_tvs' }
 \end{code}
@@ -479,31 +480,29 @@ tcGetGlobalTyVars
 zonkTcTyVars :: [TcTyVar] -> TcM [TcType]
 zonkTcTyVars tyvars = mapM zonkTcTyVar tyvars
 
-zonkTcTyVarsAndFV :: [TcTyVar] -> TcM TcTyVarSet
-zonkTcTyVarsAndFV tyvars = tyVarsOfTypes <$> mapM zonkTcTyVar tyvars
+zonkTcTyVarsAndFV :: TcTyVarSet -> TcM TcTyVarSet
+zonkTcTyVarsAndFV tyvars = tyVarsOfTypes <$> mapM zonkTcTyVar (varSetElems tyvars)
 
 -----------------  Types
 
 zonkTcTypeCarefully :: TcType -> TcM TcType
+-- Do not zonk type variables free in the environment
 zonkTcTypeCarefully ty
   = do { env_tvs <- tcGetGlobalTyVars
-       ; zonkType (zonkTcTyVarCarefully env_tvs) ty }
-
-
-zonkTcTyVarCarefully :: TcTyVarSet -> TcTyVar -> TcM TcType
--- Do not zonk type variables free in the environment
-zonkTcTyVarCarefully env_tvs tv 
-  | tv `elemVarSet` env_tvs 
-  = return (TyVarTy tv)
-  | otherwise
-  = ASSERT( isTcTyVar tv )
-    case tcTyVarDetails tv of
-      SkolemTv {}  -> return (TyVarTy tv)
-      FlatSkol ty  -> zonkType (zonkTcTyVarCarefully env_tvs) ty
-      MetaTv _ ref -> do { cts <- readMutVar ref
-                        ; case cts of    
-                            Flexi       -> return (TyVarTy tv)
-                            Indirect ty -> zonkType (zonkTcTyVarCarefully env_tvs) ty }
+       ; zonkType (zonk_tv env_tvs) ty }
+  where
+    zonk_tv env_tvs tv
+      | tv `elemVarSet` env_tvs 
+      = return (TyVarTy tv)
+      | otherwise
+      = ASSERT( isTcTyVar tv )
+       case tcTyVarDetails tv of
+         SkolemTv {}    -> return (TyVarTy tv)
+         FlatSkol ty  -> zonkType (zonk_tv env_tvs) ty
+         MetaTv _ ref   -> do { cts <- readMutVar ref
+                              ; case cts of    
+                                  Flexi       -> return (TyVarTy tv)
+                                  Indirect ty -> zonkType (zonk_tv env_tvs) ty }
 
 zonkTcType :: TcType -> TcM TcType
 -- Simply look through all Flexis
@@ -514,12 +513,29 @@ zonkTcTyVar :: TcTyVar -> TcM TcType
 zonkTcTyVar tv
   = ASSERT2( isTcTyVar tv, ppr tv )
     case tcTyVarDetails tv of
-      SkolemTv {}  -> return (TyVarTy tv)
+      SkolemTv {}    -> return (TyVarTy tv)
       FlatSkol ty  -> zonkTcType ty
-      MetaTv _ ref -> do { cts <- readMutVar ref
-                        ; case cts of    
-                            Flexi       -> return (TyVarTy tv)
-                            Indirect ty -> zonkTcType ty }
+      MetaTv _ ref   -> do { cts <- readMutVar ref
+                          ; case cts of    
+                              Flexi       -> return (TyVarTy tv)
+                              Indirect ty -> zonkTcType ty }
+
+zonkTcTypeAndSubst :: TvSubst -> TcType -> TcM TcType
+-- Zonk, and simultaneously apply a non-necessarily-idempotent substitution
+zonkTcTypeAndSubst subst ty = zonkType zonk_tv ty
+  where
+    zonk_tv tv 
+      = case tcTyVarDetails tv of
+         SkolemTv {}    -> return (TyVarTy tv)
+         FlatSkol ty    -> zonkType zonk_tv ty
+         MetaTv _ ref   -> do { cts <- readMutVar ref
+                              ; case cts of    
+                                  Flexi       -> zonk_flexi tv
+                                  Indirect ty -> zonkType zonk_tv ty }
+    zonk_flexi tv
+      = case lookupTyVar subst tv of
+          Just ty -> zonkType zonk_tv ty
+          Nothing -> return (TyVarTy tv)
 
 zonkTcTypes :: [TcType] -> TcM [TcType]
 zonkTcTypes tys = mapM zonkTcType tys
@@ -585,12 +601,12 @@ zonkQuantifiedTyVar tv
 
 \begin{code}
 zonkImplication :: Implication -> TcM Implication
-zonkImplication implic@(Implic { ic_env_tvs = env_tvs, ic_given = given 
+zonkImplication implic@(Implic { ic_untch = env_tvs, ic_given = given 
                                , ic_wanted = wanted })
-  = do { env_tvs' <- zonkTcTyVarsAndFV (varSetElems env_tvs)
+  = do { env_tvs' <- zonkTcTyVarsAndFV env_tvs
        ; given'   <- mapM zonkEvVar given
        ; wanted'  <- mapBagM zonkWanted wanted
-       ; return (implic { ic_env_tvs = env_tvs', ic_given = given'
+       ; return (implic { ic_untch = env_tvs', ic_given = given'
                         , ic_wanted = wanted' }) }
 
 zonkEvVar :: EvVar -> TcM EvVar
@@ -734,12 +750,12 @@ mkZonkTcTyVar :: (TcTyVar -> TcM Type)    -- What to do for an unbound mutable var
 mkZonkTcTyVar unbound_var_fn tyvar 
   = ASSERT( isTcTyVar tyvar )
     case tcTyVarDetails tyvar of
-      SkolemTv {}  -> return (TyVarTy tyvar)
-      FlatSkol ty  -> zonkType (mkZonkTcTyVar unbound_var_fn) ty
-      MetaTv _ ref -> do { cts <- readMutVar ref
-                        ; case cts of    
-                            Flexi       -> unbound_var_fn tyvar  
-                            Indirect ty -> zonkType (mkZonkTcTyVar unbound_var_fn) ty }
+      SkolemTv {}    -> return (TyVarTy tyvar)
+      FlatSkol ty    -> zonkType (mkZonkTcTyVar unbound_var_fn) ty
+      MetaTv _ ref   -> do { cts <- readMutVar ref
+                          ; case cts of    
+                              Flexi       -> unbound_var_fn tyvar  
+                              Indirect ty -> zonkType (mkZonkTcTyVar unbound_var_fn) ty }
 
 -- Zonk the kind of a non-TC tyvar in case it is a coercion variable 
 -- (their kind contains types).
@@ -1616,14 +1632,12 @@ sizeTypes xs               = sum (map sizeType xs)
 
 -- Size of a predicate
 --
--- Equalities are a special case.  The equality itself doesn't contribute to the
--- size and as we do not count class predicates, we have to start with one less.
--- This is easy to see considering that, given
---   class C a b | a -> b
---   type family F a
--- constraints (C a b) and (F a ~ b) are equivalent in size.
+-- We are considering whether *class* constraints terminate
+-- Once we get into an implicit parameter or equality we
+-- can't get back to a class constraint, so it's safe
+-- to say "size 0".  See Trac #4200.
 sizePred :: PredType -> Int
 sizePred (ClassP _ tys')   = sizeTypes tys'
-sizePred (IParam _ ty)     = sizeType ty
-sizePred (EqPred ty1 ty2)  = sizeType ty1 + sizeType ty2 - 1
+sizePred (IParam {})       = 0
+sizePred (EqPred {})       = 0
 \end{code}