btw: Dan Vanderkam's book "Effective TypeScript: 83 Specific Ways to Improve Your TypeScript" (which _just_ released) includes TypeScript 5.5. Even after writing TypeScript for many years I found a lot of really practically applicable stuff in it. If you like books, this is a really good one.
[1] https://www.amazon.com/Effective-TypeScript-Specific-Ways-Im...
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