Yeah, I really like zig’s approach to bitfields, everything Just Works with no faffing about with bit-shifting and OR/AND'ing. I forget the exact reason I used separate bools for rust, but I remember spending a day trying to do something zig-like and failing…

IIRC each of the #[inline] statements was tested and each made a noticable performance improvement. That’s especially true for things like RAM::get() - since the gameboy does I/O by having different chunks of RAM act differently (some address ranges are just RAM, some are hardware controls, some read data from the cartridge, etc) you can replace the hundred-line generic get() with a single instruction if you happen to know that you are looking up one hard-coded address, and that address has no special behaviour.