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.

4 files changed, 47 insertions, 39 deletions

diff --git a/unix/ffi.c b/unix/ffi.c
index ef9c6ea9d2..a25e54b54a 100644
--- a/unix/ffi.c
+++ b/unix/ffi.c
@@ -9,6 +9,7 @@
 #include "mpconfig.h"
 #include "qstr.h"
 #include "obj.h"
+#include "map.h"
 #include "runtime.h"
 #include "binary.h"
 
@@ -216,19 +217,20 @@ static mp_obj_t ffimod_make_new(mp_obj_t type_in, uint n_args, uint n_kw, const
     return o;
 }
 
-static const mp_method_t ffimod_type_methods[] = {
-        { "func", &ffimod_func_obj },
-        { "var", &ffimod_var_obj },
-        { "close", &ffimod_close_obj },
-        { NULL, NULL },
+static const mp_map_elem_t ffimod_locals_dict_table[] = {
+    { MP_OBJ_NEW_QSTR(MP_QSTR_func), (mp_obj_t) &ffimod_func_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_var), (mp_obj_t) &ffimod_var_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_close), (mp_obj_t) &ffimod_close_obj },
 };
 
+STATIC MP_DEFINE_CONST_DICT(ffimod_locals_dict, ffimod_locals_dict_table);
+
 static const mp_obj_type_t ffimod_type = {
     { &mp_type_type },
     .name = MP_QSTR_ffimod,
     .print = ffimod_print,
     .make_new = ffimod_make_new,
-    .methods = ffimod_type_methods,
+    .locals_dict = (mp_obj_t)&ffimod_locals_dict,
 };
 
 // FFI function
diff --git a/unix/file.c b/unix/file.c
index d711ace4f1..f037b6f7ea 100644
--- a/unix/file.c
+++ b/unix/file.c
@@ -9,6 +9,7 @@
 #include "mpconfig.h"
 #include "qstr.h"
 #include "obj.h"
+#include "map.h"
 #include "runtime.h"
 #include "stream.h"
 
@@ -105,16 +106,17 @@ static mp_obj_t fdfile_make_new(mp_obj_t type_in, uint n_args, uint n_kw, const
     return fdfile_new(fd);
 }
 
-static const mp_method_t rawfile_type_methods[] = {
-    { MP_QSTR_fileno, &fdfile_fileno_obj },
-    { MP_QSTR_read, &mp_stream_read_obj },
-    { MP_QSTR_readall, &mp_stream_readall_obj },
-    { MP_QSTR_readline, &mp_stream_unbuffered_readline_obj},
-    { MP_QSTR_write, &mp_stream_write_obj },
-    { MP_QSTR_close, &fdfile_close_obj },
-    { MP_QSTR_NULL, NULL },
+STATIC const mp_map_elem_t rawfile_locals_dict_table[] = {
+    { MP_OBJ_NEW_QSTR(MP_QSTR_fileno), (mp_obj_t)&fdfile_fileno_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_read), (mp_obj_t)&mp_stream_read_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_readall), (mp_obj_t)&mp_stream_readall_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_readline), (mp_obj_t)&mp_stream_unbuffered_readline_obj},
+    { MP_OBJ_NEW_QSTR(MP_QSTR_write), (mp_obj_t)&mp_stream_write_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_close), (mp_obj_t)&fdfile_close_obj },
 };
 
+STATIC MP_DEFINE_CONST_DICT(rawfile_locals_dict, rawfile_locals_dict_table);
+
 static const mp_obj_type_t rawfile_type = {
     { &mp_type_type },
     .name = MP_QSTR_io_dot_FileIO,
@@ -126,7 +128,7 @@ static const mp_obj_type_t rawfile_type = {
         .read = fdfile_read,
         .write = fdfile_write,
     },
-    .methods = rawfile_type_methods,
+    .locals_dict = (mp_obj_t)&rawfile_locals_dict,
 };
 
 // Factory function for I/O stream classes
diff --git a/unix/main.c b/unix/main.c
index e8452fd8cc..6b25988759 100644
--- a/unix/main.c
+++ b/unix/main.c
@@ -15,6 +15,7 @@
 #include "lexerunix.h"
 #include "parse.h"
 #include "obj.h"
+#include "map.h"
 #include "parsehelper.h"
 #include "compile.h"
 #include "runtime0.h"
@@ -191,17 +192,18 @@ static mp_obj_t test_set(mp_obj_t self_in, mp_obj_t arg) {
 static MP_DEFINE_CONST_FUN_OBJ_1(test_get_obj, test_get);
 static MP_DEFINE_CONST_FUN_OBJ_2(test_set_obj, test_set);
 
-static const mp_method_t test_methods[] = {
-    { MP_QSTR_get, &test_get_obj },
-    { MP_QSTR_set, &test_set_obj },
-    { MP_QSTR_NULL, NULL },
+static const mp_map_elem_t test_locals_dict_table[] = {
+    { MP_OBJ_NEW_QSTR(MP_QSTR_get), (mp_obj_t)&test_get_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_set), (mp_obj_t)&test_set_obj },
 };
 
+STATIC MP_DEFINE_CONST_DICT(test_locals_dict, test_locals_dict_table);
+
 static const mp_obj_type_t test_type = {
     { &mp_type_type },
     .name = MP_QSTR_Test,
     .print = test_print,
-    .methods = test_methods,
+    .locals_dict = (mp_obj_t)&test_locals_dict,
 };
 
 mp_obj_t test_obj_new(int value) {
diff --git a/unix/socket.c b/unix/socket.c
index 85e59b2848..3125544282 100644
--- a/unix/socket.c
+++ b/unix/socket.c
@@ -15,6 +15,7 @@
 #include "mpconfig.h"
 #include "qstr.h"
 #include "obj.h"
+#include "map.h"
 #include "objtuple.h"
 #include "objarray.h"
 #include "runtime.h"
@@ -217,28 +218,29 @@ static mp_obj_t socket_make_new(mp_obj_t type_in, uint n_args, uint n_kw, const
     return socket_new(fd);
 }
 
-static const mp_method_t microsocket_type_methods[] = {
-    { MP_QSTR_fileno, &socket_fileno_obj },
-    { MP_QSTR_makefile, &mp_identity_obj },
-    { MP_QSTR_read, &mp_stream_read_obj },
-    { MP_QSTR_readall, &mp_stream_readall_obj },
-    { MP_QSTR_readline, &mp_stream_unbuffered_readline_obj},
-    { MP_QSTR_write, &mp_stream_write_obj },
-    { MP_QSTR_connect, &socket_connect_obj },
-    { MP_QSTR_bind, &socket_bind_obj },
-    { MP_QSTR_listen, &socket_listen_obj },
-    { MP_QSTR_accept, &socket_accept_obj },
-    { MP_QSTR_recv, &socket_recv_obj },
-    { MP_QSTR_send, &socket_send_obj },
-    { MP_QSTR_setsockopt, &socket_setsockopt_obj },
-    { MP_QSTR_close, &socket_close_obj },
+static const mp_map_elem_t microsocket_locals_dict_table[] = {
+    { MP_OBJ_NEW_QSTR(MP_QSTR_fileno), (mp_obj_t)&socket_fileno_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_makefile), (mp_obj_t)&mp_identity_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_read), (mp_obj_t)&mp_stream_read_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_readall), (mp_obj_t)&mp_stream_readall_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_readline), (mp_obj_t)&mp_stream_unbuffered_readline_obj},
+    { MP_OBJ_NEW_QSTR(MP_QSTR_write), (mp_obj_t)&mp_stream_write_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_connect), (mp_obj_t)&socket_connect_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_bind), (mp_obj_t)&socket_bind_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_listen), (mp_obj_t)&socket_listen_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_accept), (mp_obj_t)&socket_accept_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_recv), (mp_obj_t)&socket_recv_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_send), (mp_obj_t)&socket_send_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_setsockopt), (mp_obj_t)&socket_setsockopt_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_close), (mp_obj_t)&socket_close_obj },
 #if MICROPY_SOCKET_EXTRA
-    { MP_QSTR_recv, &mp_stream_read_obj },
-    { MP_QSTR_send, &mp_stream_write_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_recv), (mp_obj_t)&mp_stream_read_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_send), (mp_obj_t)&mp_stream_write_obj },
 #endif
-    { MP_QSTR_NULL, NULL },
 };
 
+STATIC MP_DEFINE_CONST_DICT(microsocket_locals_dict, microsocket_locals_dict_table);
+
 static const mp_obj_type_t microsocket_type = {
     { &mp_type_type },
     .name = MP_QSTR_socket,
@@ -250,7 +252,7 @@ static const mp_obj_type_t microsocket_type = {
         .read = socket_read,
         .write = socket_write,
     },
-    .methods = microsocket_type_methods,
+    .locals_dict = (mp_obj_t)&microsocket_locals_dict,
 };
 
 static mp_obj_t mod_socket_htons(mp_obj_t arg) {