unexpected-access-proxy.ts

const UNEXPECTED_ACCESS = Symbol() as never
export function throwsOnUnexpectedAccess<T extends object>(target: T): T {
  return new Proxy(target, {
    get: (target, key) => {
      const value = target[key as keyof typeof target]
      if (value === UNEXPECTED_ACCESS) {
        throw new Error(`Unexpected access to "${String(key)}"`)
      }
      return value
    },
  })
}