anchor.diff:  library polymorphic.grind;
   
  +import "dart:io";
  +
   import "package:grinder/grinder.dart";
  +import "package:yaml/yaml.dart";
   
   void main(List<String> args) {
     task("clean", defaultClean);
  
positive.code: 
  package(GrinderContext context) {
    ensureOutDirectory();
    
    var args = [
      "--enable-experimental-mirrors",
  
negative.code:   if (!dir.existsSync()) {
      dir.createSync(recursive: true);
    }
  }
  