specExpr subst (Type ty) = returnSM (Type (substTy subst ty), emptyUDs)
specExpr subst (Var v) = returnSM (specVar subst v, emptyUDs)
specExpr subst (Lit lit) = returnSM (Lit lit, emptyUDs)
specExpr subst (Type ty) = returnSM (Type (substTy subst ty), emptyUDs)
specExpr subst (Var v) = returnSM (specVar subst v, emptyUDs)
specExpr subst (Lit lit) = returnSM (Lit lit, emptyUDs)