Remove mp_obj_type_t.methods entry and use .locals_dict instead.

Originally, .methods was used for methods in a ROM class, and
locals_dict for methods in a user-created class.  That distinction is
unnecessary, and we can use locals_dict for ROM classes now that we have
ROMable maps.

This removes an entry in the bloated mp_obj_type_t struct, saving a word
for each ROM object and each RAM object.  ROM objects that have a
methods table (now a locals_dict) need an extra word in total (removed
the methods pointer (1 word), no longer need the sentinel (2 words), but
now need an mp_obj_dict_t wrapper (4 words)).  But RAM objects save a
word because they never used the methods entry.

Overall the ROM usage is down by a few hundred bytes, and RAM usage is
down 1 word per user-defined type/class.

There is less code (no need to check 2 tables), and now consistent with
the way ROM modules have their tables initialised.

Efficiency is very close to equivaluent.

1 files changed, 8 insertions, 7 deletions

diff --git a/stmhal/dac.c b/stmhal/dac.c
index bc86e07bdf..caf8beeecb 100644
--- a/stmhal/dac.c
+++ b/stmhal/dac.c
@@ -260,20 +260,21 @@ mp_obj_t pyb_dac_dma(uint n_args, const mp_obj_t *args, mp_map_t *kw_args) {
 
 STATIC MP_DEFINE_CONST_FUN_OBJ_KW(pyb_dac_dma_obj, 3, pyb_dac_dma);
 
-STATIC const mp_method_t pyb_dac_methods[] = {
-    { MP_QSTR_noise, &pyb_dac_noise_obj },
-    { MP_QSTR_triangle, &pyb_dac_triangle_obj },
-    { MP_QSTR_write, &pyb_dac_write_obj },
-    { MP_QSTR_dma, &pyb_dac_dma_obj },
+STATIC const mp_map_elem_t pyb_dac_locals_dict_table[] = {
+    { MP_OBJ_NEW_QSTR(MP_QSTR_noise), (mp_obj_t)&pyb_dac_noise_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_triangle), (mp_obj_t)&pyb_dac_triangle_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_write), (mp_obj_t)&pyb_dac_write_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_dma), (mp_obj_t)&pyb_dac_dma_obj },
     // TODO add function that does double buffering:
     //  dma2(freq, buf1, buf2, callback)
     //  where callback is called when the buffer has been drained
-    { MP_QSTR_NULL, NULL },
 };
 
+STATIC MP_DEFINE_CONST_DICT(pyb_dac_locals_dict, pyb_dac_locals_dict_table);
+
 const mp_obj_type_t pyb_dac_type = {
     { &mp_type_type },
     .name = MP_QSTR_DAC,
     .make_new = pyb_dac_make_new,
-    .methods = pyb_dac_methods,
+    .locals_dict = (mp_obj_t)&pyb_dac_locals_dict,
 };