anchor.diff:          return new PrecompilerCompilerConfiguration(
               isDebug: isDebug,
               isChecked: isChecked,
  -            isProduct: isProduct,
               arch: configuration['arch']);
         case 'none':
           return new NoneCompilerConfiguration(
  
positive.code:     // which can eventually completely replace the Map-based configuration
      // object.
      bool isDebug = configuration['mode'] == 'debug';
      bool isProduct = configuration['mode'] == 'product';
      bool isChecked = configuration['checked'];
      bool isHostChecked = configuration['host_checked'];
      bool useSdk = configuration['use_sdk'];
  
negative.code: 
  class PrecompilerCompilerConfiguration extends CompilerConfiguration {
    final String arch;
  
    PrecompilerCompilerConfiguration({bool isDebug, bool isChecked, String arch})
        : super._subclass(isDebug: isDebug, isChecked: isChecked),
          arch = arch;
  
    int computeTimeoutMultiplier() {
  