anchor.diff:  
     /// Create a hash set containing all [elements].
     ///
  -  /// Creates a hash set as by `new HashSet<E>()` and adds all given [elements]
  +  /// Creates a hash set as by `HashSet<E>()` and adds all given [elements]
     /// to the set. The elements are added in order. If [elements] contains
     /// two entries that are equal, but not identical, then the first one is
     /// the one in the resulting set.
  +  /// Example:
  +  /// ```dart
  +  /// final baseSet = <int>{1, 2, 3};
  +  /// final hashSetOf = HashSet<num>.of(baseSet);
  +  /// print(hashSetOf); // fx {3, 1, 2}
  +  /// ```
     factory HashSet.of(Iterable<E> elements) => HashSet<E>()..addAll(elements);
   
     /// Provides an iterator that iterates over the elements of this set.
     ///
     /// The order of iteration is unspecified,
  -  /// but consistent between changes to the set.
  +  /// but is consistent between changes to the set.
     Iterator<E> get iterator;
   }
  
positive.code:   /// instance of [E], which means that:
    /// ```dart template:expression
    /// HashSet<int>(equals: (int e1, int e2) => (e1 - e2) % 5 == 0,
    ///              hashCode: (int e) => e % 5)
    /// ```
    /// does not need an `isValidKey` argument because it defaults to only
    /// accepting `int` values which are accepted by both `equals` and `hashCode`.
  
negative.code: 
    /// Creates an unordered identity-based set.
    ///
    /// Effectively shorthand for:
    /// ```dart
    /// HashSet<E>(equals: identical, hashCode: identityHashCode)
    /// ```
  