X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FInst.lhs;h=e175951d9517375c49fa56cd60115f7e8ea319e9;hb=25f84fa7e4b84c3db5ba745a7881c009b778e0b1;hp=8d21d1bcb190b8973b99d40035e75f5c8e8a7b94;hpb=7fc749a43b4b6b85d234fa95d4928648259584f4;p=ghc-hetmet.git

diff --git a/compiler/typecheck/Inst.lhs b/compiler/typecheck/Inst.lhs
index 8d21d1b..e175951 100644
--- a/compiler/typecheck/Inst.lhs
+++ b/compiler/typecheck/Inst.lhs
@@ -48,7 +48,7 @@ module Inst (
 
 	mkWantedCo, mkGivenCo,
 	fromWantedCo, fromGivenCo,
-	eitherEqInst, mkEqInst, mkEqInsts,
+	eitherEqInst, mkEqInst, mkEqInsts, mkWantedEqInst,
 	finalizeEqInst, writeWantedCoercion,
 	eqInstType, updateEqInstCoercion,
 	eqInstCoercion,
@@ -1004,6 +1004,12 @@ 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 <- newMetaTyVar TauTv (mkCoKind ty1 ty2)
+       ; mkEqInst pred (Left cotv)
+       }
+
 -- type inference:
 --	We want to promote the wanted EqInst to a given EqInst
 --	in the signature context.