coercion

class Contract
  INVALID = Object.new.freeze

  COERCERS = {
    string: ->(v) { v.is_a?(String) ? v : v.to_s },
    integer: ->(v) { Integer(v.to_s) rescue INVALID },

import { z } from "zod";

const coerceNumber = z.preprocess((v) => {
  if (v === "" || v === undefined) return undefined;
  if (typeof v !== "string") return v;
  const n = Number(v);