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