code: public final boolean synpred22_InternalPureXbase() {
          state.backtracking++;
          int start = input.mark();
          try {
              synpred22_InternalPureXbase_fragment(); // can never throw exception
          } catch (RecognitionException re) {
              System.err.println("impossible: "+re);
          }
          boolean success = !state.failed;
          input.rewind(start);
          state.backtracking--;
          state.failed=false;
          return success;
      }
docs: Delegated rules