bpo-37540: vectorcall: keyword names must be strings (GH-14682)



The fact that keyword names are strings is now part of the vectorcall and `METH_FASTCALL` protocols. The biggest concrete change is that `_PyStack_UnpackDict` now checks that and raises `TypeError` if not.

CC @markshannon @vstinner 


https://bugs.python.org/issue37540
diff --git a/Doc/c-api/object.rst b/Doc/c-api/object.rst
index 2cf0328..fd1e9c6 100644
--- a/Doc/c-api/object.rst
+++ b/Doc/c-api/object.rst
@@ -400,8 +400,8 @@
    :c:func:`PyVectorcall_NARGS(nargsf) <PyVectorcall_NARGS>`.
 
    *kwnames* can be either NULL (no keyword arguments) or a tuple of keyword
-   names. In the latter case, the values of the keyword arguments are stored
-   in *args* after the positional arguments.
+   names, which must be strings. In the latter case, the values of the keyword
+   arguments are stored in *args* after the positional arguments.
    The number of keyword arguments does not influence *nargsf*.
 
    *kwnames* must contain only objects of type ``str`` (not a subclass),