Definition REFLEXIVITYTAC : rtac typ (expr typ func) :=
fun tus tvs n m c s e =>
  match e with
| (App (App (Inj (inr (Other (feq ty)))) l) r) =>
  match @exprUnify (ctx_subst c) typ func _ _ _ _ _ 3
                                 tus tvs 0 l r ty s with
    | Some su => RTac.Core.Solved su
    | None =>  RTac.Core.Fail
  end
| _ => RTac.Core.Fail
end.

Lemma REFLEXIVITYTAC_sound : rtac_sound (Expr_expr := func_defs.Expr_expr_fs tbl) REFLEXIVITYTAC.