ABAP 740 - Collect usando FOR GROUP

TYPES: BEGIN OF tp_t,
         matnr TYPE matnr,
         tipo  type char1,
         cont  TYPE i,
       END OF tp_t.

types gkey type TABLE OF tp_t WITH DEFAULT KEY.

DATA t_teste TYPE TABLE OF tp_t.

APPEND VALUE #( matnr = 'A' cont = 1 ) TO t_teste.
APPEND VALUE #( matnr = 'A' cont = 1 ) TO t_teste.
APPEND VALUE #( matnr = 'B' tipo = 'X' cont = 1 ) TO t_teste.
APPEND VALUE #( matnr = 'B' cont = 2 ) TO t_teste.
APPEND VALUE #( matnr = 'B' cont = 3 ) TO t_teste.
APPEND VALUE #( matnr = 'D' cont = 2 ) TO t_teste.
APPEND VALUE #( matnr = 'C' cont = 1 ) TO t_teste.
APPEND VALUE #( matnr = 'C' cont = 1 ) TO t_teste.
APPEND VALUE #( matnr = 'C' tipo = 'W' cont = 1 ) TO t_teste.
APPEND VALUE #( matnr = 'C' tipo = 'W' cont = 1 ) TO t_teste.

data(lt_mat) =
  VALUE gkey(
    FOR GROUPS material OF wa IN t_teste
    GROUP BY ( matnr = wa-matnr
               tipo = wa-tipo )
               DESCENDING
               LET cont_1 = REDUCE tp_t( init line type tp_t
                                     for ls_c in group material
                                     NEXT line-matnr = ls_c-matnr
                                          LINE-TIPO = ls_c-tipo
                                          line-cont = line-cont + ls_c-cont ) in ( cont_1 ) ).


BREAK-POINT.

LOOP AT lt_mat INTO data(lsx).
  WRITE: / lsx-matnr, lsx-tipo, lsx-cont.
ENDLOOP.