anchor.diff:    /// decreases the preferred width. The preferred width is the value that
     /// would be returned by [getMinIntrinsicWidth] for that height.
     ///
  +  /// The width argument may give a specific width to assume. The given width
  +  /// can be infinite, meaning that the intrinsic height in an unconstrained
  +  /// environment is being requested. The given width should never be negative
  +  /// or null.
  +  ///
     /// This function should only be called on one's children. Calling this
     /// function couples the child with the parent so that when the child's layout
     /// changes, the parent is notified (via [markNeedsLayout]).
  
positive.code:   /// [computeMinIntrinsicHeight].
    @mustCallSuper
    double getMinIntrinsicHeight(double width) {
      return _computeIntrinsicDimension(_IntrinsicDimension.minHeight, width, computeMinIntrinsicHeight);
    }
  
  
negative.code:   /// If the layout algorithm is strictly height-in-width-out, or is
    /// height-in-width-out when the width is unconstrained, then the height
    /// argument is the height to use.
    ///
    /// The `height` argument will never be negative or null. It may be infinite.
    ///
    /// If this algorithm depends on the intrinsic dimensions of a child, the
    /// intrinsic dimensions of that child should be obtained using the functions
  