Missing constant color highlighting inside `stringify!`

[MariaSolOs]

rust-analyzer version: 0.3.1435-standalone (f1e51af 2023-03-12)

rustc version: 1.70.0-nightly (ff4b772 2023-03-10)

relevant settings: Shouldn't be relevant to the bug per se, but I'm using this color theme.

While experimenting with macro_rules, I found the following weird behavior:

For some reason, when using an all-caps snake-case argument with the stringify!() macro that begins with a single all-cap letter followed by an underscore (I know, this is such a niche case that I won't be hurt if this gets backlogged forever), the corresponding argument isn't properly highlighted. I suspect this is an issue with semantic tokens (?) since the inspector shows the following:

[lowr]

Done a bit of investigation: we don't provide any semantic information for tokens inside stringify!() (or any tokens that we could not determine its semantics). Those textmate scopes seem to come from the grammar definition VSCode provides (as a fallback I guess?), which has been converted from another repo.

[Veykril]

There is nothing in the output that would map to the input tokens of the stringify call so we can't resolve the inputs either. Because of that we don't tag the inputs at all which makes VSCode fallback to the textmate grammar

[MariaSolOs]

That makes sense. Now my question for @dustypomerleau (hi! 👋🏻) is: Why have the restriction on the first two characters being a letter? I see before this commit the restriction was only on the first letter.

I'm not exactly suggesting that we change this BTW, I'm just curious to learn more about the naming convention.