Provide a ReadonlyRegExp type

Search Terms

readonlyregexp readonly regexp

Suggestion

Provide a new ReadonlyRegExp type that represents a read only RegExp.

Use Cases

This is similar to other readonly types, e.g. ReadonlyArray -- I prefer my code to be immutable by default. I have a DeepReadonly helper that could map RegExp to ReadonlyRegExp.

Note that Readonly<RegExp> does not work:

'a'.replace(/a/ as Readonly<RegExp>, 'b')

/*
No overload matches this call.
  The last overload gave the following error.
    Argument of type 'Readonly<RegExp>' is not assignable to parameter of type 'string | RegExp'.
      Type 'Readonly<RegExp>' is missing the following properties from type 'RegExp': [Symbol.match], [Symbol.replace], [Symbol.search], [Symbol.split](2769)
*/

Examples

const emailRegExp = /[a-z]@[a-z\.]/ as ReadonlyRegExp;

export function suppressPII(message: string) {
    return message.replace(emailRegExp, '');
}

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.

この issue には実装ファイル、テスト、エントリポイントが記載されていません。まず、TypeScript が RegExp と既存の readonly 型をどのように宣言しているかを追跡し、次に、示されている replace の例に必要な宣言および互換性の変更を特定してください。完了条件は、ReadonlyRegExp 型が利用可能で、例が RegExp を想定している箇所で使用できることです。