Ken Jin <kenjin4096@gmail.com> added the comment: To answer the person who posted this on docs mailing list, after much investigation, it seems that this made it into 3.7.0, 3.5.4 and 3.6.2 . Here's the 3.7.0 (alpha) commit for the initial implementation of typing.NoReturn: https://github.com/python/cpython/commit/f06e0218ef6007667f5d61184b85a81a046... The backport to 3.6 (at the time, this was 3.6.2rc1): https://github.com/python/cpython/commit/e612c28513b406779d187e5f816445c7d40... The backport to 3.5 (at the time, this was 3.5.4rc1): https://github.com/python/cpython/commit/4b15e45895ca56ac5f7837cacb8cd3ccc26... I'm sorry if I got anything wrong (this is somewhat confusing for me too). ---------- _______________________________________ Python tracker <report@bugs.python.org> <https://bugs.python.org/issue43978> _______________________________________