gistfile1.txt

  Fmt.(pf ppf "type %s = {@[<v>@,%a@;<1 -2>@]}" name (list ~sep:(any ";@ ") gen_record_field))

result:

    type t = {
              bar : BarEnum;
              baz : BazMsg;
              bum : BazMsg.Data;
              foomap : (BarEnum * BazMsg)
            }

  Fmt.(pf ppf "type %s = {@;<1 2>@[<v>%a@;<1 -2>@]}" name (list ~sep:(any ";@ ") gen_record_field))

result:

    type t = {
      bar : BarEnum;
      baz : BazMsg;
      bum : BazMsg.Data;
      foomap : (BarEnum * BazMsg)
    }