Distant sighting of macro annotations

I’ve been busy with work, and most stuff happening in the Dotty repos these days is straightforward bug fixes and enhancements. But seriously intriguing stuff still crops up now and then.

The latest is this very early-stage PR for macro annotations. There is no documentation, so you sort of have to know what you’re looking for, but the various unit tests provide a hint of the potential here — they are mostly trivial little “hello, world” experiments (many of them explicitly so), but they demonstrate various ways in which a macro annotation on something can muck around with it. (The most interesting tests in terms of figuring out what is going on can be found under tests/run-macros.)

The usual caveat applies in spades here: this is just a draft PR, and I’m not aware of even a pre-SIP for this yet. But it’s ferociously exciting — folks have been wanting a reasonably principled macro-annotation approach for Scala 3 for years now. Fingers crossed that this experiment pays off…