Properly ppr InstEqs in wanteds of implication constraints

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

diff --git a/compiler/typecheck/Inst.lhs b/compiler/typecheck/Inst.lhs
index 1032f91..da80df4 100644 (file)
--- a/compiler/typecheck/Inst.lhs
+++ b/compiler/typecheck/Inst.lhs
@@ -52,8 +52,7 @@ module Inst (
        eitherEqInst, mkEqInst, mkEqInsts, mkWantedEqInst,
        finalizeEqInst, writeWantedCoercion,
        eqInstType, updateEqInstCoercion,
-       eqInstCoercion,
-       eqInstLeftTy, eqInstRightTy
+       eqInstCoercion, eqInstTys
     ) where
 
 #include "HsVersions.h"
@@ -99,6 +98,8 @@ import Outputable
 import Data.List
 import TypeRep
 import Class
+
+import Control.Monad ( liftM )
 \end{code}
 
 
@@ -139,7 +140,7 @@ instType imp@(ImplicInst {})      = mkImplicTy (tci_tyvars imp) (tci_given imp)
 instType (EqInst {tci_left = ty1, tci_right = ty2}) = mkPredTy (EqPred ty1 ty2)
 
 mkImplicTy tvs givens wanteds  -- The type of an implication constraint
-  = ASSERT( all isDict givens )
+  = ASSERT( all isAbstractableInst givens )
     -- pprTrace "mkImplicTy" (ppr givens) $
     -- See [Equational Constraints in Implication Constraints]
     let dict_wanteds = filter (not . isEqInst) wanteds
@@ -555,11 +556,11 @@ zonkInst implic@(ImplicInst {})
 
 zonkInst eqinst@(EqInst {tci_left = ty1, tci_right = ty2})
   = do { co' <- eitherEqInst eqinst 
-                       (\covar -> return (mkWantedCo covar)) 
-                       (\co    -> zonkTcType co >>= \coercion -> return (mkGivenCo coercion))
+                 (\covar -> return (mkWantedCo covar)) 
+                 (\co    -> liftM mkGivenCo $ zonkTcType co)
        ; ty1' <- zonkTcType ty1
        ; ty2' <- zonkTcType ty2
-       ; return (eqinst {tci_co = co',tci_left=ty1',tci_right=ty2})
+       ; return (eqinst {tci_co = co', tci_left= ty1', tci_right = ty2' })
        }
 
 zonkInsts insts = mappM zonkInst insts
@@ -602,11 +603,14 @@ pprInst i@(EqInst {tci_left = ty1, tci_right = ty2, tci_co = co})
                (\covar -> text "Wanted" <+> ppr (TyVarTy covar) <+> dcolon <+> ppr (EqPred ty1 ty2))
                (\co    -> text "Given"  <+> ppr co              <+> dcolon <+> ppr (EqPred ty1 ty2))
 pprInst inst = ppr (instName inst) <+> dcolon 
-               <+> (braces (ppr (instType inst)) $$
+               <+> (braces (ppr (instType inst) <> implicWantedEqs) $$
                     ifPprDebug implic_stuff)
   where
-    implic_stuff | isImplicInst inst = ppr (tci_reft inst)
-                | otherwise         = empty
+    (implic_stuff, implicWantedEqs) 
+      | isImplicInst inst = (ppr (tci_reft inst),
+                            text " &" <+> 
+                            ppr (filter isEqInst (tci_wanted inst)))
+      | otherwise        = (empty, empty)
 
 pprInstInFull inst@(EqInst {}) = pprInst inst
 pprInstInFull inst = sep [quotes (pprInst inst), nest 2 (pprInstArising inst)]
@@ -1050,9 +1054,8 @@ eqInstType inst = eitherEqInst inst mkTyVarTy id
 eqInstCoercion :: Inst -> Either TcTyVar Coercion
 eqInstCoercion = tci_co
 
-eqInstLeftTy, eqInstRightTy :: Inst -> TcType
-eqInstLeftTy  = tci_left
-eqInstRightTy = tci_right
+eqInstTys :: Inst -> (TcType, TcType)
+eqInstTys inst = (tci_left inst, tci_right inst)
 
 updateEqInstCoercion :: (Either TcTyVar Coercion -> Either TcTyVar Coercion) -> Inst -> Inst
 updateEqInstCoercion f inst = inst {tci_co = f $ tci_co inst}