anchor.diff:        return;
       }
   
  +    var importCache = new ImportCache([],
  +        loadPaths: options.loadPaths, logger: options.logger);
       for (var source in options.sourcesToDestinations.keys) {
         var destination = options.sourcesToDestinations[source];
         try {
  -        await _compileStylesheet(options, source, destination);
  +        await _compileStylesheet(options, importCache, source, destination);
         } on SassException catch (error, stackTrace) {
           printError(error.toString(color: options.color),
               options.trace ? stackTrace : null);
  
positive.code: 
  /// Compiles the stylesheet at [source] to [destination].
  ///
  /// If [source] is `null`, that indicates that the stylesheet should be read
  /// from stdin. If [destination] is `null`, that indicates that the stylesheet
  /// should be emitted to stdout.
  Future _compileStylesheet(
      ExecutableOptions options, String source, String destination) async {
    SingleMapping sourceMap;
    var sourceMapCallback =
        options.emitSourceMap ? (SingleMapping map) => sourceMap = map : null;
  
    var indented =
        options.indented ?? (source != null && p.extension(source) == '.sass');
    var text = source == null ? await readStdin() : readFile(source);
    var url = source == null ? null : p.toUri(source);
    var importer = new FilesystemImporter('.');
    String css;
    if (options.asynchronous) {
      css = await compileStringAsync(text,
          indented: indented,
          logger: options.logger,
          style: options.style,
          importer: importer,
          loadPaths: options.loadPaths,
          url: url,
          sourceMap: sourceMapCallback);
    } else {
      css = compileString(text,
          indented: indented,
          logger: options.logger,
          style: options.style,
          importer: importer,
          loadPaths: options.loadPaths,
          url: url,
          sourceMap: sourceMapCallback);
    }
  
    css += _writeSourceMap(options, sourceMap, destination);
    if (destination == null) {
      if (css.isNotEmpty) print(css);
    } else {
      ensureDir(p.dirname(destination));
      writeFile(destination, css + "\n");
    }
  }
  
  /// Writes the source map given by [mapping] to disk (if necessary) according to
  
negative.code: import 'package:stack_trace/stack_trace.dart';
  
  import '../sass.dart';
  import 'ast/sass.dart';
  import 'async_import_cache.dart';
  import 'exception.dart';
  import 'executable_options.dart';
  import 'import_cache.dart';
  import 'io.dart';
  import 'util/path.dart';
  import 'visitor/async_evaluate.dart';
  import 'visitor/evaluate.dart';
  import 'visitor/serialize.dart';
  
  main(List<String> args) async {
    var printedError = false;
  