anchor.diff:    /// children because constructing the [List] requires doing work for every
     /// child that could possibly be displayed in the list view instead of just
     /// those children that are actually visible.
  +  ///
  +  /// It is usually more efficient to create children on demand using [new
  +  /// ListView.builder].
     ListView({
       Key key,
       Axis scrollDirection: Axis.vertical,
  
positive.code:   /// number of children because the builder is called only for those children
    /// that are actually visible.
    ///
    /// Providing a non-null [itemCount] improves the ability of the [GridView] to
    /// estimate the maximum scroll extent.
    ///
    /// [itemBuilder] will be called only with indices greater than or equal to
    /// zero and less than [itemCount].
    ///
    /// The [gridDelegate] argument must not be null.
    GridView.builder({
  
negative.code:   /// number of children because the builder is called only for those children
    /// that are actually visible.
    ///
    /// Providing a non-null `itemCount` improves the ability of the [ListView] to
    /// estimate the maximum scroll extent.
    ///
    /// The `itemBuilder` callback will be called only with indices greater than
    /// or equal to zero and less than `itemCount`.
    ///
    /// The `itemBuilder` should actually create the widget instances when called.
    /// Avoid using a builder that returns a previously-constructed widget; if the
    /// list view's children are created in advance, or all at once when the
    /// [ListView] itself is created, it is more efficient to use [new ListView].
    /// Even more efficient, however, is to create the instances on demand using
    /// this constructor's `itemBuilder` callback.
    ListView.builder({
      Key key,
      Axis scrollDirection: Axis.vertical,
  