py: Check that sequence has 2 elements for dict iterable constructor.

py/obj.c

@@ -280,7 +280,7 @@ void mp_obj_get_array_fixed_n(mp_obj_t o, uint len, mp_obj_t **items) {
             mp_obj_list_get(o, &seq_len, items);
         }
         if (seq_len != len) {
-            nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_IndexError, "requested length %d but object has length %d", len, seq_len));
+            nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError, "requested length %d but object has length %d", len, seq_len));
         }
     } else {
         nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_TypeError, "object '%s' is not a tuple or list", mp_obj_get_type_str(o)));

py/objdict.c

@@ -50,9 +50,11 @@ STATIC mp_obj_t dict_make_new(mp_obj_t type_in, uint n_args, uint n_kw, const mp
             mp_obj_t iterable = mp_getiter(args[0]);
             mp_obj_t dict = mp_obj_new_dict(0);
             // TODO: support arbitrary seq as a pair
-            mp_obj_tuple_t *item;
+            mp_obj_t item;
             while ((item = mp_iternext(iterable)) != MP_OBJ_NULL) {
-                mp_obj_dict_store(dict, item->items[0], item->items[1]);
+                mp_obj_t *sub_items;
+                mp_obj_get_array_fixed_n(item, 2, &sub_items);
+                mp_obj_dict_store(dict, sub_items[0], sub_items[1]);
             }
             return dict;
         }

tests/basics/dict-from-iter.py

@@ -2,3 +2,13 @@ print(dict([(1, "foo")]))
 d = dict([("foo", "foo2"), ("bar", "baz")])
 print(sorted(d.keys()))
 print(sorted(d.values()))
+
+try:
+    dict(((1,),))
+except ValueError:
+    print("ValueError")
+
+try:
+    dict(((1, 2, 3),))
+except ValueError:
+    print("ValueError")