anchor.diff:  
   uses_tabs
       : 'usesTabs' '=' NUMBER ';'
  +    ;
  +
  +platform_filter
  +    : 'platformFilter' '=' (QUOTED_STRING|NON_QUOTED_STRING) ';'
       ;
   
   children
  
positive.code: pbx_build_file
      : REFERENCE '=' '{'
          isa_pbx_build_file
          file_ref
          settings?
        '}' ';'
      ;
  
negative.code: 
  file_ref
      : 'fileRef' '=' REFERENCE ';'
      ;
  
  product_ref
      : 'productRef' '=' REFERENCE ';'
      ;
  
  container_portal
  