closes#19737ref:#19737 (comment)---It's not the prettiest code, but since it will be removed once PEP 800gets accepted (or rejected), I figured it would be best to keep itsimple, so that we can easily revert it.

It is time to announce this (as still experimental obviously).(cherry picked from commitd33c147)

This PR adds 2 new weakref primitives for weakref.proxy (1 and 2 arg)(cherry picked from commit8f2371a)

Incorrect processing in detect_undefined_bitmap could cause a ValueErrorexception in emit_undefined_attr_check.

(cherry picked from commitfd05265)

(cherry picked from commit9ae3e9a)

Did various edits, added a few additional sections, and reordered somesections.(cherry picked from commit73fa69e)

Remove Unreleased from section title(cherry picked from commitf0863a5)

Fixes#19836Fix is trivial, I am surprised none of the existing tests caught this inthe original PR. After this is merged, I am going to add the test to`master`.

…__ (#19733)Fixes#19732This is a simple check to point users in the right direction when theyget errors because their class uses `__new__` but they wrote stubs for`__init__`. I don't feel strongly about the exact wording used here. Ialso considered "Maybe you meant to define `__new__` instead of`__init__`?".(cherry picked from commit530bdc5)

if a variable is Final but the value is not yet known at compile-time,and that variable is used as an input to an f-string, the f-string willincorrectly contain "None"Fixes [mypyc#1140](mypyc/mypyc#1140)(cherry picked from commitdce8e1c)

…Any` (#14708)

Changelog update for 1.18.2Also updated the changelog to reflect the initial release being 1.18.1,since we had to bump the version due to wheels failing.This adds the cherry picked PRs mentioned in#19764 (comment)(cherry picked from commit4301be1)