Fix deriving of indexed data types

- Fix typo introduced when moving deriving-specific code from TcEnv to TcDeriv
- Thanks to Roman for the bug report

diff --git a/compiler/typecheck/TcDeriv.lhs b/compiler/typecheck/TcDeriv.lhs
index 4e1a065..6934eb1 100644 (file)
--- a/compiler/typecheck/TcDeriv.lhs
+++ b/compiler/typecheck/TcDeriv.lhs
@@ -426,7 +426,7 @@ tcLookupFamInstExact tycon tys
   = do { result@(rep_tycon, rep_tys) <- tcLookupFamInst tycon tys
        ; let { tvs                   = map (Type.getTyVar 
                                                "TcDeriv.tcLookupFamInstExact") 
-                                           tys
+                                           rep_tys
             ; variable_only_subst = all Type.isTyVarTy rep_tys &&
                                     sizeVarSet (mkVarSet tvs) == length tvs
                                        -- renaming may have no repetitions