Window functions: wrong sort criteria is used

create table t1 (a int, b int, c int);

insert into t1 values (1,3,1),(2,2,1),(3,1,1);

explain format=json

select 

  rank() over (partition by c order by a),

  count(*) over (partition by c)

from t1;

  "query_block": {

    "select_id": 1,

    "window_functions_computation": {

      "sorts": {

        "filesort": {

          "sort_key": "t1.c"

        }

      },

      "temporary_table": {

        "table": {

          "table_name": "t1",

          "access_type": "ALL",

          "rows": 3,

          "filtered": 100

        }

      }

    }

  }

(gdb) p dbug_print_item(prev)

  $103 = 0x555556d7e280 "count(*) over (partition by c)"

(gdb) p prev->marker

  $104 = 7

(gdb) p dbug_print_item(curr)

  $105 = 0x555556d7e280 "rank() over (partition by c order by a)"

(gdb) p curr->marker

  $106 = 0