I'm aware that this isn't on the roadmap (T4157, et al), but I'd find it incredibly helpful as we liberally use 5.4  syntax at WePay, and attempting to roll our own parse tree using token_get_all would be... not a great idea. This makes both linters and symbol importing tedious at best (non-reusable state machines, manual brace matching, and plenty of other not-fun-stuff). Granted the symbol stuff still gets a little confused when it comes to namespaces, but that's unrelated to this.
I'm quite happy to take this on myself if will actually be accepted, but I don't want to waste time trying if it's something that won't actually be supported, i.e. D1207, so this mostly serves to gauge interest (is there a better forum for this?)
 short-array syntax and traits are problems; it seems to handle namespaces and closures just fine. We're not on 5.5 yet due to an apc change, so I'll leave yield and finally alone for now.