The article explains most of this, but the key takeaway for beginners once this lands is: With `become` you can write tail calls in Rust and it will promise they either work or don't compile, you can't have the case (which exists in several languages) where you thought you'd written a tail call but you hadn't (or maybe you had but you switched to a different compiler or made a seemingly inconsequential change to the code) and now the stack has overflowed.

Rust has been really good at providing ergonomic support for features we're too used to seeing provided as "Experts only" features with correspondingly poor UX.

From the first line of the post:

> Last week, I wrote a tail-call interpreter using the become keyword, which was recently added to nightly Rust (seven months ago is recent, right?).