anchor.diff:    var hashes = <String, Map>{};
     for (var channel in supportedChannels) {
       hashes[channel] = {};
  -    for (var file in _files[channel]) {
  -      var hash = await _getHash256(channel, revisions[channel], file);
  -      hashes[channel][file] = hash;
  +    for (var files in _files[channel]) {
  +      for (var file in files.values) {
  +        var hash = await _getHash256(channel, revisions[channel], file);
  +        hashes[channel][file] = hash;
  +      }
       }
     }
     return hashes;
  
positive.code:   homepage "https://www.dartlang.org/"
  
    version "$stableVersion"
    if Hardware::CPU.is_64_bit?
      url "$_urlBase/stable/release/${revisions['stable']}/$_x64File"
      sha256 "${hashes['stable'][_x64File]}"
    else
      url "$_urlBase/stable/release/${revisions['stable']}/$_ia32File"
      sha256 "${hashes['stable'][_ia32File]}"
    end
  
    devel do
      version "$devVersion"
      if Hardware::CPU.is_64_bit?
        url "$_urlBase/dev/release/${revisions['dev']}/$_x64File"
        sha256 "${hashes['dev'][_x64File]}"
      else
        url "$_urlBase/dev/release/${revisions['dev']}/$_ia32File"
        sha256 "${hashes['dev'][_ia32File]}"
      end
    end
  
  
negative.code: part of '../update_homebrew.dart';
  
  const _files = {
    'dev': [_x64Files, _ia32Files],
    'stable': [_x64Files, _ia32Files]
  };
  
  const _urlBase = 'https://storage.googleapis.com/dart-archive/channels';
  const _x64Files = {
    'mac': 'sdk/dartsdk-macos-x64-release.zip',
    'linux': 'sdk/dartsdk-linux-x64-release.zip',
  };
  const _ia32Files = {
    'mac': 'sdk/dartsdk-macos-ia32-release.zip',
    'linux': 'sdk/dartsdk-linux-ia32-release.zip',
  };
  
  Future<String> _getHash256(
      String channel, String revision, String download) async {
  