anchor.diff:   */
   const Matcher returnsNormally = const _ReturnsNormally();
   
  -class _Throws extends BaseMatcher {
  +class Throws extends BaseMatcher {
     final Matcher _matcher;
   
  -  const _Throws([Matcher matcher]) :
  +  const Throws([Matcher matcher]) :
       this._matcher = matcher;
   
     bool matches(item, MatchState matchState) {
  
positive.code: 
  /** A matcher for functions that throw IndexOutOfRangeException */
  const Matcher throwsIndexOutOfRangeException =
      const _Throws(isIndexOutOfRangeException);
  
  class _IndexOutOfRangeException extends _ExceptionMatcher {
    const _IndexOutOfRangeException() : super("IndexOutOfRangeException");
    bool matches(item, MatchState matchState) => item is IndexOutOfRangeException;
  }
  
negative.code: 
  /** A matcher for functions that throw NoSuchMethodError */
  const Matcher throwsNoSuchMethodError =
      const Throws(isNoSuchMethodError);
  
  class _NoSuchMethodError extends ExceptionMatcher {
    const _NoSuchMethodError() : super("NoSuchMethodError");
    bool matches(item, MatchState matchState) => item is NoSuchMethodError;
  }
  