+-- TEMPORARY FIX
+-- (DontBind,DontBind)
+-- -> failTc (unifyDontBindErr tv1 ps_ty2)
+
+-- TEMPORARILY allow two type-sig variables to be bound together.
+-- See notes in tcCheckSigVars
+ (DontBind,DontBind) | kind2 `hasMoreBoxityInfo` kind1
+ -> tcWriteTyVar tv1 ty2 `thenNF_Tc_` returnTc ()
+
+ | kind1 `hasMoreBoxityInfo` kind2
+ -> tcWriteTyVar tv2 (TyVarTy tv1) `thenNF_Tc_` returnTc ()
+