py: Add MP_OBJ_STOP_ITERATION and make good use of it.

Also make consistent use of MP_OBJ_NOT_SUPPORTED and MP_OBJ_NULL.
This helps a lot in debugging and understanding of function API.

1 files changed, 3 insertions, 3 deletions

diff --git a/py/objtuple.c b/py/objtuple.c
index 57b313fd6..e6b902d74 100644
--- a/py/objtuple.c
+++ b/py/objtuple.c
@@ -52,7 +52,7 @@ mp_obj_t mp_obj_tuple_make_new(mp_obj_t type_in, uint n_args, uint n_kw, const m
 
             mp_obj_t iterable = mp_getiter(args[0]);
             mp_obj_t item;
-            while ((item = mp_iternext(iterable)) != MP_OBJ_NULL) {
+            while ((item = mp_iternext(iterable)) != MP_OBJ_STOP_ITERATION) {
                 if (len >= alloc) {
                     items = m_renew(mp_obj_t, items, alloc, alloc * 2);
                     alloc *= 2;
@@ -88,7 +88,7 @@ mp_obj_t tuple_unary_op(int op, mp_obj_t self_in) {
     switch (op) {
         case MP_UNARY_OP_BOOL: return MP_BOOL(self->len != 0);
         case MP_UNARY_OP_LEN: return MP_OBJ_NEW_SMALL_INT(self->len);
-        default: return MP_OBJ_NULL; // op not supported for None
+        default: return MP_OBJ_NOT_SUPPORTED;
     }
 }
 
@@ -249,7 +249,7 @@ STATIC mp_obj_t tuple_it_iternext(mp_obj_t self_in) {
         self->cur += 1;
         return o_out;
     } else {
-        return MP_OBJ_NULL;
+        return MP_OBJ_STOP_ITERATION;
     }
 }