Make assignTemp_ less pessimistic

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

diff --git a/compiler/types/TypeRep.lhs b/compiler/types/TypeRep.lhs
index 446341d..db41403 100644 (file)
--- a/compiler/types/TypeRep.lhs
+++ b/compiler/types/TypeRep.lhs
@@ -145,11 +145,12 @@ data Type
                        --    can appear as the right hand side of a type synonym.
 
   | FunTy
-       Type
+       Type            
        Type            -- ^ Special case of 'TyConApp': @TyConApp FunTyCon [t1, t2]@
+                       -- See Note [Equality-constrained types]
 
   | ForAllTy
-       TyCoVar         -- ^ Type *or* coercion variable; see Note [Equality-constrained types]
+       TyCoVar         -- Type variable
        Type            -- ^ A polymorphic type
 
   | PredTy
@@ -183,21 +184,9 @@ The type   forall ab. (a ~ [b]) => blah
 is encoded like this:
 
    ForAllTy (a:*) $ ForAllTy (b:*) $
-   ForAllTy (wild_co : a ~ [b]) $
+   FunTy (PredTy (EqPred a [b]) $
    blah
 
-That is, the "(a ~ [b]) =>" part is encode as a for-all
-type with a coercion variable that is never mentioned.
-
-We could instead have used a FunTy with an EqPred on the 
-left.  But we want 
-
-  * FunTy to mean RUN-TIME abstraction,
-    passing a real value at runtime, 
-
-  * ForAllTy to mean COMPILE-TIME abstraction, 
-    erased at runtime
-
 -------------------------------------
                Note [PredTy]
 
@@ -567,9 +556,7 @@ instance Outputable name => OutputableBndr (IPName name) where
        -- OK, here's the main printer
 
 ppr_type :: Prec -> Type -> SDoc
-ppr_type _ (TyVarTy tv)         -- Note [Infix type variables]
-  | isSymOcc (getOccName tv)  = parens (ppr tv)
-  | otherwise                = ppr tv
+ppr_type _ (TyVarTy tv)              = ppr_tvar tv
 ppr_type p (PredTy pred)      = maybeParen p TyConPrec $
                                 ifPprDebug (ptext (sLit "<pred>")) <> (pprPredTy pred)
 ppr_type p (TyConApp tc tys)  = pprTcApp p ppr_type tc tys
@@ -605,17 +592,22 @@ ppr_forall_type p ty
     split2 ps (PredTy p `FunTy` ty) = split2 (p:ps) ty
     split2 ps ty                   = (reverse ps, ty)
 
+ppr_tvar :: TyVar -> SDoc
+ppr_tvar tv  -- Note [Infix type variables]
+  | isSymOcc (getOccName tv)  = parens (ppr tv)
+  | otherwise                = ppr tv
+
 -------------------
 pprForAll :: [TyVar] -> SDoc
 pprForAll []  = empty
 pprForAll tvs = ptext (sLit "forall") <+> sep (map pprTvBndr tvs) <> dot
 
 pprTvBndr :: TyVar -> SDoc
-pprTvBndr tv
-  | isLiftedTypeKind kind = ppr tv
-  | otherwise             = parens (ppr tv <+> dcolon <+> pprKind kind)
-  where
-    kind = tyVarKind tv
+pprTvBndr tv 
+  | isLiftedTypeKind kind = ppr_tvar tv
+  | otherwise            = parens (ppr_tvar tv <+> dcolon <+> pprKind kind)
+            where
+              kind = tyVarKind tv
 \end{code}
 
 Note [Infix type variables]