Using nullish coalescing with untyped field in constructor trigger TS7022

Bug Report

Using nullish coalescing in a constructor to initialize a class member with no type annotation will result in a TS7022 error.

🔎 Search Terms

nullish, coalescing, 7022, ??, and ts7022

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about nullish coalescing and type inference.

⏯ Playground Link

Playground link with relevant code

💻 Code

export class Node {
  #parent

  #children = new Children(this)

  constructor (parent?: Node | null | undefined) {
    // Remove `??` and the code after and the code compiled. Now #parent is undefined which is not desired.
    this.#parent = parent ?? null
  }

  get parent () { return this.#parent }

  get children () { return this.#children }
}

export class Children {
  #parent
  #head
  #tail

  constructor (parent: Node) {
    this.#parent = parent
    this.#head = new Node(parent)
    this.#tail = new Node(parent)
  }
}

🙁 Actual behavior

Attempting to compile the example code results in a TS7022 error: '#parent' implicitly has type 'any' because it does not have a type annotation and is referenced directly or indirectly in its own initializer.

🙂 Expected behavior

The code should compile and #parent should be typed as Node | null.

Reproduisez le problème avec le TypeScript Playground lié et les classes Node et Children fournies. Suivez la gestion par le compilateur des champs privés non typés et de la coalescence des valeurs nulles autour de TS7022 ; le travail est terminé lorsque l’exemple se compile et que #parent est inféré comme Node | null sans annotation.