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function message(msg: string, actual: unknown, ...types: string[]) {  if (types.length > 2) {    const last = types.pop()    msg += `one of type ${types.join(', ')}, or ${last}.`  } else if (types.length === 2) {    msg += `one of type ${types[0]} or ${types[1]}.`  } else {    msg += `of type ${types[0]}.`  }
  if (actual == null) {    msg += ` Received ${actual}`  } else if (typeof actual === 'function' && actual.name) {    msg += ` Received function ${actual.name}`  } else if (typeof actual === 'object' && actual != null) {    if (actual.constructor?.name) {      msg += ` Received an instance of ${actual.constructor.name}`    }  }
  return msg}
export default (actual: unknown, ...types: string[]) => {  return message('Key must be ', actual, ...types)}
export function withAlg(alg: string, actual: unknown, ...types: string[]) {  return message(`Key for the ${alg} algorithm must be `, actual, ...types)}