add explanatory comment

diff --git a/Python/compile.c b/Python/compile.c
index 44ced73c958f7df85a156b40ee7232850c7faf0f..917f9d3b12e564e58ff4173b6fa583b8fde7565c 100644 (file)
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -3769,6 +3769,8 @@ dict_keys_inorder(PyObject *dict, int offset)
                return NULL;
        while (PyDict_Next(dict, &pos, &k, &v)) {
                i = PyInt_AS_LONG(v);
+               /* The keys of the dictionary are tuples. (see compiler_add_o)
+                  The object we want is always first, though. */
                k = PyTuple_GET_ITEM(k, 0);
                Py_INCREF(k);
                assert((i - offset) < size);