class MyPromise<T = void> extends Promise<T> {
  started = false
  resolve: (t: T) => void = () => {}
  reject: (e: any) => void = () => {}
  constructor() {
    console.log('constructor')
    let resolve: (t: T) => void = () => {}
    let reject: (e: any) => void = () => {}
    super((res, rej) => {
      resolve = res
      reject = rej
    })
    this.resolve = resolve
    this.reject = reject
  }
}

const thing = new MyPromise<string>()
thing.resolve('a')
thing.then(t => console.log('then', t))

Constructor is called twice and I get this error

constructor
constructor
[TestError] TypeError: Promise resolve or reject function is not callable

Running on node 14.17.1