ts-r
  • Sound mode S-08, pre-alpha
  • Design record 0007, Accepted

TSR0803

'this' escapes from the constructor through '{0}' before subclass fields are initialised. Make it '#private', or do this after construction (a static factory).

A constructor calls an overridable method or passes 'this' out, before subclass fields exist. Make the method #private or use a static factory.

Rule S-08: Fields are initialised before `this` escapes (level: sound). Reported by ts-r-check and ts-r-lsp in files that opt in to sound mode. See Sound mode.

What it means

A subclass's fields aren't initialised until the base constructor returns, so a base constructor that calls a method a subclass can override (or passes this out) can run subclass code on a half-built object. #private and private members are allowed, because their bodies are checked by the same rule.

Example

Spec case from design record 0007 (checked by the record's case harness, not by this site's build)
// A base constructor calls a method a subclass can override.
class Base {
  constructor() {
    this.setup(); // @expect TSR0803
  }
  setup(): void {
    console.log("base");
  }
}
new Base();
export {};

How to fix

  • Make the helper #private.
  • Replace two-phase initialisation with a static factory that constructs, then calls the setup method.

Sound mode is defined in design record 0007 (accepted 2026-10-15).