anchor.diff:  /// Changing the [StreamBuilder] configuration to another stream during event
   /// generation introduces snapshot pairs of the form
   ///
  -/// * `AsyncSnapshot<int>.withData(ConnectionState.none, 5)`
  -/// * `AsyncSnapshot<int>.withData(ConnectionState.waiting, 5)`
  +/// * `new AsyncSnapshot<int>.withData(ConnectionState.none, 5)`
  +/// * `new AsyncSnapshot<int>.withData(ConnectionState.waiting, 5)`
   ///
   /// The latter will be produced only when the new stream is non-null. The former
   /// only when the old stream is non-null.
   ///
   /// The stream may produce errors, resulting in snapshots of the form
   ///
  -/// * `AsyncSnapshot<int>.withError(ConnectionState.active, 'some error')`
  +/// * `new AsyncSnapshot<int>.withError(ConnectionState.active, 'some error')`
   ///
   /// The data and error fields of snapshots produced are only changed when the
   /// state is `ConnectionState.active`.
  
positive.code: ///
  /// ## Sample code
  ///
  /// This sample shows a button used to initiate an asynchronous computation
  /// with a string result, and a text label reflecting the progress:
  ///
  /// ```dart
  /// class Calculator extends StatefulWidget {
  ///   @override
  ///   _CalculatorState createState() => new _CalculatorState();
  /// }
  ///
  /// class _CalculatorState extends State<Calculator> {
  ///   Future<String> _calculation;
  ///
  ///   void _initiateCalculation() {
  ///     setState(() {
  ///       _calculation = new Future.delayed(const Duration(seconds: 2), () => 'long awaited');
  ///     });
  ///   }
  ///
  ///   Widget _buildCalculationWidget(BuildContext context, AsyncSnapshot<String> snapshot) {
  ///     switch (snapshot.connectionState) {
  ///       case ConnectionState.none: return new Text('Press button to start');
  ///       case ConnectionState.waiting: return new Text('Awaiting result...');
  
negative.code: /// old future has already completed successfully with data as above, changing
  /// configuration to a new future results in snapshot pairs of the form:
  ///
  /// * `new AsyncSnapshot<String>.withData(ConnectionState.none, 'some data')`
  /// * `new AsyncSnapshot<String>.withData(ConnectionState.waiting, 'some data')`
  ///
  /// In general, the latter will be produced only when the new future is
  /// non-null. The former only when the old future is non-null.
  