Many of us had given up hope that what ended being the "Inferred Predicate Types" feature of this release could ever be possible... and in the end, it was just like 10 lines of code!!
If you like technical deep dives on new TypeScript features, we did just such a deep dive[1] on this feature's PR with the author himself, Dan Vanderkam. He goes through how he got the idea and motivation for what ended up being a really creative fix.
[1] https://youtu.be/LTuzl2r2HjA
