Allow usage of `Reflect.get()` by returning `unknown` instead of `any`

Search Terms

Reflect get unknown

Suggestion

Change the type definition of Reflect.get() to return unknown instead of any.

Use Cases

Allow type safe dynamic access of fields on an object or { [k: string}: unknown }

Using Reflect.get(o, 'some key') and have it return unknown.

This allows usage of Reflect.get() in code bases where we do not want implicit any and where we have @typescript-eslint rules to ban unsafe usage of any.

Examples

/**
 * @param {CustomError} cause
 * @returns {{ [k: string]: unknown }}
 */
function getInfoForPlainError (cause) {
  /** @type {{ [k: string]: unknown }} */
  const info = {}
  for (const field of PLAIN_ERROR_FIELDS) {
    const v = reflectGet(cause, field)
    if (typeof v !== 'undefined') {
      info[field] = v
    }
  }
  return info
}

Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

Unfortunately changing a signature from any to unknown is a breaking change.

まず、Reflect.get の lib.d.ts 宣言と、推論される戻り値の型を対象とするテストを見つけます。any を unknown に変更すると既存の型チェックの期待値にどのような影響があるかを確認します。宣言と関連するテストが、要求された戻り値の型を一貫してサポートしていれば完了です。