anchor.diff:          i++;
   
           c = line[i];
  -        String mapped = ESCAPE_MAPPING[c];
  -        if (mapped == null) mapped = c;
  +        String mapped = ESCAPE_MAPPING[c] ?? c;
           buffer.write(mapped);
           continue;
         }
       }
  -    if (!inQuotes && c == " ") {
  -      if (buffer.isNotEmpty) result.add(buffer.toString());
  -      buffer.clear();
  +    if (!inQuotes && c == ' ') {
  +      if (buffer.isNotEmpty) {
  +        result.add(buffer.toString());
  +        buffer.clear();
  +      }
         continue;
       }
       buffer.write(c);
     }
  -  if (inQuotes) throw new FormatException("Unclosed quotes: $line");
  +  if (inQuotes) throw new FormatException('Unclosed quotes: $line');
     if (buffer.isNotEmpty) result.add(buffer.toString());
     return result;
   }
  
positive.code: // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
  // for details. All rights reserved. Use of this source code is governed by a
  // BSD-style license that can be found in the LICENSE file.
  
  library dart2js.util.command_line;
  
  /// The accepted escapes in the input of the --batch processor.
  ///
  /// Contrary to Dart strings it does not contain hex escapes (\u or \x).
  Map<String, String> ESCAPE_MAPPING = const {
    "n": "\n",
    "r": "\r",
    "t": "\t",
    "b": "\b",
    "f": "\f",
    "v": "\v",
    "\\": "\\",
  };
  
  /// Splits the line similar to how a shell would split arguments. If [windows]
  /// is `true` escapes will be handled like on the Windows command-line.
  ///
  /// Example:
  ///
  ///     splitline("""--args "ab"c 'with " \'spaces'""").forEach(print);
  ///     // --args
  ///     // abc
  ///     // with " 'spaces
  List<String> splitLine(String line, {bool windows: false}) {
    List<String> result = <String>[];
    bool inQuotes = false;
    String openingQuote;
    StringBuffer buffer = new StringBuffer();
    for (int i = 0; i < line.length; i++) {
      String c = line[i];
  
negative.code:     }
      if (c == '\\') {
        if (i == line.length - 1) {
          throw new FormatException('Unfinished escape: $line');
        }
        if (windows) {
          String next = line[i + 1];
  