Type for values defined and used in {@link HasAutoHorizontalAlignment}. Defined here so that HorizontalAlignmentConstant can be derived from it, thus allowing HasAutoHorizontalAlignment methods to accept and return both AutoHorizontalAlignmentConstant and HorizontalAlignmentConstant values - without allowing the methods defined here to accept or return AutoHorizontalAlignmentConstant values.

class AutoHorizontalAlignmentConstant{
 // The constructor is package-private to prevent uncontrolled inheritance
 // and instantiation of this class.
 const AutoHorizontalAlignmentConstant.internal();
}