docs: Expression XreadRowValueConstructor() {
  
          Expression e;
  
          e = XreadExplicitRowValueConstructorOrNull();
  
          if (e != null) {
              return e;
          }
  
          e = XreadRowOrCommonValueExpression();
  
          if (e != null) {
              return e;
          }
  
          return XreadBooleanValueExpression();
      }