Description

class Sprite {
  name = "";
 
  constructor(name: string) {
    this.name = name;
  }
}

type Constructor = new (...args: any[]) => {};
 
function Scale<TBase extends Constructor>(Base: TBase) {
  return class Scaling extends Base {
    _scale = 1;
 
    setScale(scale: number): this {
      this._scale = scale;
      return this;
    }
  };
}

export const A = Scale(Sprite);

declare class Sprite {
    name: string;
    constructor(name: string);
}
export declare const A: {
    new (...args: any[]): {
        _scale: number;
// A 'this' type is available only in a non-static member of a class or interface.ts(2526)
        setScale(scale: number): this;
    };
} & typeof Sprite;
export {};

Contributor guide

Tech stack

typescript

Domain

tooling

Issue type

bug

DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.

5

Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.

over 1 week

Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.

stale

ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.

clear

Prerequisites

TypeScript's type systemmixins and constructor typescompiler emit pipeline

Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.

15

Research direction

Investigate the TypeScript compiler's emit logic for declaration files (src/compiler/emit.ts). Focus on how the 'this' type is handled for anonymous classes inside mixin functions. The error TS2526 occurs when a method returns 'this' inside an anonymous class in a DTS. Examine the existing test suite for similar issues. Look at PRs or comments on the issue for any hints. Ensure that the emitted DTS does not contain the error for valid TS code.