anchor.diff:                .readAsString()));
   
     PubSpec copy({String name, String author, Version version, String homepage,
  -      String documentation, String description,
  +      String documentation, String description, Environment environment,
         Map<String, DependencyReference> dependencies,
         Map<String, DependencyReference> devDependencies,
         Map<String, DependencyReference> dependencyOverrides, Map unParsedYaml}) {
  
positive.code:       ..add('version', version)
        ..add('homepage', homepage)
        ..add('documentation', documentation)
        ..add('description', description)
        ..add('dependencies', dependencies)
        ..add('dev_dependencies', devDependencies)
  
negative.code:   @override
    Map toJson() {
      return (buildJson
        ..add('sdk', "'${sdkConstraint.toString()}'")
        ..addAll(unParsedYaml)).json;
    }
  }
  