[feature] class properties that are "readonly in public, writable in private" or other permutations

Search Terms

typescript readonly on the outside writable on the inside

• https://stackoverflow.com/questions/46634876/how-can-i-change-a-readonly-property-in-typescript

Suggestion

Some sort of syntax to describe readonly on the outside, writeable on the inside for a given property, so we can avoid making a getter just for this purpose (or using any of the convoluted options linked in that StackOverflow post).

Use Cases

To make this pattern easier to express.

Examples

instead of having to write

class Foo {
  private _foo = 123
  get foo() {
    return this._foo
  }

  changeIt() {
    this._foo = 456
  }
}

const f = new Foo
f.foo = 345 // ERROR

we would be able to write something shorter like

class Foo {
  publicread foo = 123

  changeIt() {
    this.foo = 456
  }
}

const f = new Foo
f.foo = 345 // ERROR

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.

Aucun fichier, test ou point d’entrée n’est nommé. Commencez par examiner la syntaxe proposée, l’exemple basé sur un getter et la discussion de 66 commentaires afin de comprendre les permutations non résolues et les contraintes de conception. Le travail serait considéré comme terminé lorsqu’un accord sur la syntaxe de la fonctionnalité et son comportement de vérification des types aura été trouvé avant de pouvoir définir le périmètre de l’implémentation.