code: public void rawWarning(int pos, String msg) {
          PrintWriter warnWriter = writers.get(WriterKind.ERROR);
          if (nwarnings < MaxWarnings && emitWarnings) {
              printRawDiag(warnWriter, "warning: ", pos, msg);
          }
          prompt();
          nwarnings++;
          warnWriter.flush();
      }
docs: report a warning: