anchor.diff:  external double sin(num radians);
   external double sqrt(num radians);
   external double tan(num radians);
  +
   class Random {
     bool nextBool() => true;
     double nextDouble() => 2.0;
     int nextInt() => 1;
   }
  +
   class Point<T extends num> {}
   ''',
       )
  
positive.code:   void add(E value) {}
    void addAll(Iterable<E> iterable) {}
    void clear() {}
  
    noSuchMethod(Invocation invocation) => null;
  }
  
  class Map<K, V> {
    factory Map() => null;
    factory Map.fromIterable(Iterable iterable,
        {K key(element), V value(element)}) => null;
    Iterable<K> get keys => null;
    int get length => 0;
    Iterable<V> get values => null;
    V operator [](K key) => null;
    void operator []=(K key, V value) {}
    Map<RK, RV> cast<RK, RV>() => null;
    bool containsKey(Object key) => false;
  }
  
negative.code: 
    Future<R> then<R>(FutureOr<R> onValue(T value)) => null;
    Future<T> whenComplete(action());
  
    static Future<List<T>> wait<T>(Iterable<Future<T>> futures) => null;
  }
  
  