proposition: Lemma map_expr_size_subst_all_map_expr defs m : map_expr_size (subst_all subst_map_expr m defs) = map_expr_size m.
proof: Proof. induction defs; simpl; auto. destruct a. now rewrite map_expr_size_subst_map_expr. Qed.
imports: Coq.NArith.NArith Coq.FSets.FMaps Coq.micromega.Lia Category.Lib Category.Lib.FMapExt