anchor.diff:    FieldNames get fieldNames => builder.fieldNames;
   
     InitializerBuilder(this.builder, this.environment) {
  -    expressionBuilder = new ExpressionBuilder(builder, environment);
  +    expressionBuilder =
  +        new StatementBuilder(builder, environment).expressionBuilder;
     }
   
     void build(Initializer node) {
  
positive.code:   }
  
    int _makeDeclarationSiteFieldInitializer(Field field) {
      return new ExpressionBuilder(this, new Environment(this, null, field))
          .build(field.initializer);
    }
  
    void buildConstructor(Class hostClass, Constructor node) {
  
negative.code:   FieldNames get names => builder.fieldNames;
  
    StatementBuilder(this.builder, this.environment) {
      expressionBuilder = new ExpressionBuilder(builder, this, environment);
    }
  
    Completion build(Statement node) => node.accept(this);
  