AsyncResult, a Rusty Result in Typescript, for fun.

async-result.ts

export class AsyncResult<T, E extends Error = any> {
  private constructor(private readonly value?: T, private readonly error?: E) {}

  public static Ok<T, E extends Error>(value: T) {
    return new AsyncResult<T, E>(value);
  }

  public static Err<T, E extends Error>(error: E) {
    return new AsyncResult<T, E>(undefined, error);
  }

  public unwrap(): T {
    if (this.value && this.error === undefined) {
      return this.value;
    } else {
      // Painc
      const error = new Error();
      error.message = this.error!.message;
      error.stack = this.error!.stack;
      error.name = this.error!.name;
      throw error;
    }
  }

  public isOk(): boolean {
    return this.value !== undefined;
  }

  public isErr(): boolean {
    return !this.isOk();
  }

  public unwrapOr(value: T): T {
    if (this.value) {
      return this.value;
    } else {
      return value;
    }
  }

  public unwrapOrElse(fn: () => T) {
    if (this.value) {
      return this.value;
    } else {
      return fn();
    }
  }
}