docs: private void fromExpression(PatternDescrBuilder<?> pattern) throws RecognitionException {
          String expr = conditionalOrExpression();
          if (state.failed)
              return;
  
          if (state.backtracking == 0) {
              pattern.from().expression(expr);
              if (input.LA(1) != DRL6Lexer.EOF) {
                  helper.emit(Location.LOCATION_LHS_BEGIN_OF_CONDITION);
              }
          }
      }