Overhaul of the rewrite rules

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

diff --git a/compiler/typecheck/Inst.lhs b/compiler/typecheck/Inst.lhs
index 279ddec..9c152e1 100644 (file)
--- a/compiler/typecheck/Inst.lhs
+++ b/compiler/typecheck/Inst.lhs
@@ -6,11 +6,11 @@
 The @Inst@ type: dictionaries or method instances
 
 \begin{code}
-{-# OPTIONS_GHC -w #-}
+{-# OPTIONS -w #-}
 -- The above warning supression flag is a temporary kludge.
 -- While working on this module you are encouraged to remove it and fix
 -- any warnings in the module. See
---     http://hackage.haskell.org/trac/ghc/wiki/WorkingConventions#Warnings
+--     http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
 -- for details
 
 module Inst ( 
@@ -42,13 +42,14 @@ module Inst (
        isTyVarDict, isMethodFor, 
 
        zonkInst, zonkInsts,
-       instToId, instToVar, instType, instName,
+       instToId, instToVar, instType, instName, instToDictBind,
+       addInstToDictBind,
 
        InstOrigin(..), InstLoc, pprInstLoc,
 
        mkWantedCo, mkGivenCo,
        fromWantedCo, fromGivenCo,
-       eitherEqInst, mkEqInst, mkEqInsts,
+       eitherEqInst, mkEqInst, mkEqInsts, mkWantedEqInst,
        finalizeEqInst, writeWantedCoercion,
        eqInstType, updateEqInstCoercion,
        eqInstCoercion,
@@ -91,6 +92,7 @@ import PrelNames
 import BasicTypes
 import SrcLoc
 import DynFlags
+import Bag
 import Maybes
 import Util
 import Outputable
@@ -205,6 +207,15 @@ tyVarsOfInst (EqInst {tci_left = ty1, tci_right = ty2}) = tyVarsOfType ty1 `unio
 
 tyVarsOfInsts insts = foldr (unionVarSet . tyVarsOfInst) emptyVarSet insts
 tyVarsOfLIE   lie   = tyVarsOfInsts (lieToList lie)
+
+
+--------------------------
+instToDictBind :: Inst -> LHsExpr TcId -> TcDictBinds
+instToDictBind inst rhs 
+  = unitBag (L (instSpan inst) (VarBind (instToId inst) rhs))
+
+addInstToDictBind :: TcDictBinds -> Inst -> LHsExpr TcId -> TcDictBinds
+addInstToDictBind binds inst rhs = binds `unionBags` instToDictBind inst rhs
 \end{code}
 
 Predicates
@@ -979,11 +990,10 @@ fromWantedCo :: String -> Either TcTyVar Coercion -> TcTyVar
 fromWantedCo _ (Left covar) = covar
 fromWantedCo msg _         = panic ("fromWantedCo: not a wanted coercion: " ++ msg)
 
-eitherEqInst 
-       :: Inst                 -- given or wanted EqInst
-       -> (TcTyVar  -> a)      --      result if wanted
-       -> (Coercion -> a)      --      result if given
-       -> a            
+eitherEqInst :: Inst               -- given or wanted EqInst
+            -> (TcTyVar  -> a)     --  result if wanted
+            -> (Coercion -> a)     --  result if given
+            -> a               
 eitherEqInst (EqInst {tci_co = either_co}) withWanted withGiven
        = case either_co of
                Left  covar -> withWanted covar
@@ -1004,6 +1014,12 @@ mkEqInst (EqPred ty1 ty2) co
             }
        where mkName uniq src_span = mkInternalName uniq (mkVarOcc "co") src_span
 
+mkWantedEqInst :: PredType -> TcM Inst
+mkWantedEqInst pred@(EqPred ty1 ty2)
+  = do { cotv <- newMetaCoVar ty1 ty2
+       ; mkEqInst pred (Left cotv)
+       }
+
 -- type inference:
 --     We want to promote the wanted EqInst to a given EqInst
 --     in the signature context.