guard-class.ts

class Guard<T> {
  constructor(public value: T) {}
  isNotArray(): Guard<T extends any[] ? never : T> {
    return Array.isArray(this.value) ? new Guard<never>(undefined as never) : this as unknown as Guard<T extends any[] ? never : T>;
  }
  isNotUndefined(): Guard<Exclude<T, undefined>> {
    return this.value === undefined ? new Guard<never>(undefined as never) : this as unknown as Guard<Exclude<T, undefined>>;
  }
  isNotBoolean(): Guard<Exclude<T, boolean>> {
    return typeof this.value === 'boolean' ? new Guard<never>(undefined as never) : this as unknown as Guard<Exclude<T, boolean>>;
  }
  isArray(): Guard<Extract<T, any[]>> {
    return Array.isArray(this.value) ? this as unknown as Guard<Extract<T, any[]>> : new Guard<never>(undefined as never);
  }
}