Distinct optimization produces broken sql query

    String statement = "SELECT\n" +
                       "  DISTINCT \"case-column\"\n" +
                       "FROM (\n" +
                       "   SELECT \n" +
                       "   CASE\n" +
                       "      WHEN CAST(? AS VARCHAR) = \"ENAME\" THEN CAST(? AS INTEGER)\n" +
                       "      ELSE CAST(? AS INTEGER)\n" +
                       "      END AS \"case-column\"\n" +
                       "   FROM \"EMP\")";

    CalciteAssert.model(JdbcTest.SCOTT_MODEL)
        .query(statement)
        .consumesPreparedStatement(p -> {
          p.setString(1, "name");
          p.setInt(2, 2);
          p.setInt(3, 1);
        })
        .planHasSql("");

SELECT
  DISTINCT "case-column"
FROM
   SELECT 
   CASE
      WHEN CAST(? AS VARCHAR) = "store_name" THEN CAST(? AS INTEGER)
      ELSE CAST(? AS INTEGER)
      END AS "case-column"
   FROM "foodmart"."store"

SELECT
   CASE
      WHEN ? = "ENAME" THEN ?
      ELSE ?
   END AS "case-column"
FROM
   "SCOTT"."EMP"
GROUP BY
   CASE
      WHEN ? = "ENAME" THEN ?
      ELSE ?
   END