A little refactoring, plus improve error locations

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

diff --git a/compiler/typecheck/TcDeriv.lhs b/compiler/typecheck/TcDeriv.lhs
index 3466cbf..5d2b829 100644 (file)
--- a/compiler/typecheck/TcDeriv.lhs
+++ b/compiler/typecheck/TcDeriv.lhs
@@ -440,8 +440,7 @@ deriveStandalone (L loc (DerivDecl deriv_ty))
               <+> text "tvs:" <+> ppr tvs
               <+> text "theta:" <+> ppr theta
               <+> text "tau:" <+> ppr tau)
-       ; (cls, inst_tys) <- checkValidInstHead tau
-       ; checkValidInstance tvs theta cls inst_tys
+       ; (cls, inst_tys) <- checkValidInstance deriv_ty tvs theta tau
                -- C.f. TcInstDcls.tcLocalInstDecl1
 
        ; let cls_tys = take (length inst_tys - 1) inst_tys