TS2333: 'this' cannot be referenced in constructor arguments

Suggestion

✅ Viability 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, new syntax sugar for JS, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

⭐ Suggestion

TypeScript disallows this:

class A {
    constructor(readonly b: B = new B(this)) {}
}
class B {
    constructor(a: A) {}
}

TS2333: 'this' cannot be referenced in constructor arguments

Instead, we can rewrite it as follows.

class A {
    readonly b: B;
    constructor(b?: B) {
        this.b = b ?? new B(this);
    }
}
class B {
    constructor(a: A) {}
}

However, this is clearly more verbose. Since this transformation is always possible, it seems TypeScript should allow this in the constructor and be doing the job of rewriting it for us, so we can maintain simpler code using the former constructor argument approach.

📃 Motivating Example

Permitting this references in constructor arguments simplifies object initialization.

💻 Use Cases

Creating classes at construction time that reference the creating class.

Beginnen Sie damit, die TS2333-Diagnose und die Prüfungen des Compilers für this in Konstruktorargumenten nachzuverfolgen; das Issue nennt keine bestimmten Dateien oder Tests. Vergleichen Sie die vorgeschlagenen Konstruktorbeispiele mit dem erzeugten JavaScript und dem bestehenden Verhalten der Typprüfung, und ziehen Sie Tests in Betracht, die festlegen, wann die Referenz akzeptiert werden sollte, ohne die Laufzeitausgabe zu ändern.