TS1243

'static' modifier cannot be used with 'abstract' modifier.

Broken Code ❌

abstract class CustomNumber {
  static abstract getNumber(): number;
}

You cannot define a function that is static and abstract. You have to keep it static:

Fixed Code ✔️

abstract class CustomNumber {
  static getNumber(): number {
    return 1337;
  }
}

'async' modifier cannot be used with 'abstract' modifier.

Broken Code ❌

abstract async goto(): Promise<void>;

Fixed Code ✔️

abstract goto(): Promise<void>;