anchor.diff:    /// Any time the queue would produce an element that is not a [T],
     /// the element access will throw.
     ///
  -  /// Any time a [T] value is attempted stored into the adapted queue,
  -  /// the store will throw unless the value is also an instance of [S].
  +  /// When a [T] value is stored into the adapted queue,
  +  /// the operation will throw unless the value is also an instance of [S].
     ///
     /// If all accessed elements of [source] are actually instances of [T],
  -  /// and if all elements stored into the returned queue are actually instance
  +  /// and if all elements stored into the returned queue are actually instances
     /// of [S],
     /// then the returned queue can be used as a `Queue<T>`.
     ///
     /// Methods which accept `Object?` as argument, like [contains] and [remove],
  -  /// will pass the argument directly to the this queue's method
  +  /// will pass the argument directly to this queue's method
     /// without any checks.
     static Queue<T> castFrom<S, T>(Queue<S> source) => CastQueue<S, T>(source);
   
  
positive.code:   /// that is not an instance of [R], the access will throw instead.
    ///
    /// Elements added to the queue (e.g., by using [addFirst] or [addAll])
    /// must be instance of [R] to be valid arguments to the adding function,
    /// and they must be instances of [E] as well to be accepted by
    /// this queue as well.
    ///
    /// Methods which accept `Object?` as argument, like [contains] and [remove],
  
negative.code:   /// Adds [value] at the end of the queue.
    void add(E value);
  
    /// Removes a single instance of [value] from the queue.
    ///
    /// Returns `true` if a value was removed, or `false` if the queue
    /// contained no element equal to [value].
  