code: @SuppressWarnings({ "unchecked", "rawtypes" })
      public static <D> SimpleExpression<D> constantAs(D source, Path<D> alias) {
          if (source == null) {
              return as((Expression) nullExpression(), alias);
          } else {
              return as(ConstantImpl.create(source), alias);
          }
      }
docs: Create a {@code source as alias} expression
  
  @param source source
  @param alias alias
  @return source as alias