anchor.diff:    /**
      * Return the [ImportDirective] node that corresponds to the [element].
      */
  -  Future<ImportDirective> _findNode() async {
  -    // TODO(brianwilkerson) Determine whether this await is necessary.
  -    await null;
  +  ImportDirective _findNode() {
       LibraryElement library = element.library;
       String path = library.source.fullName;
  -    CompilationUnit unit = (await session.getParsedUnit(path)).unit;
  +    CompilationUnit unit = session.getParsedUnit(path).unit;
       int index = library.imports.indexOf(element);
       return unit.directives.where((d) => d is ImportDirective).toList()[index];
     }
  
positive.code:    * an [InterpolationExpression] without surrounding curly brackets, return it.
     * Otherwise return `null`.
     */
    Future<SimpleIdentifier> _getInterpolationIdentifier(
        SourceReference reference) async {
      // TODO(brianwilkerson) Determine whether this await is necessary.
      await null;
      Source source = reference.element.source;
      CompilationUnit unit = session.getParsedUnit(source.fullName).unit;
      NodeLocator nodeLocator = new NodeLocator(reference.range.offset);
  
negative.code:         reference.addEdit(change, '');
        } else {
          SimpleIdentifier interpolationIdentifier =
              _getInterpolationIdentifier(reference);
          if (interpolationIdentifier != null) {
            doSourceChange_addElementEdit(
                change,
  