parse use bounds (precise capture syntax)

[m4rch3n1ng]

fn capture(&self) -> impl Iterator<Item = usize> + use<'_> {}

currently tree-sitter-rust says that the use capture bound is a generic_type type_identifier, but after this it is a use_bounds use.

announced here, documented here and specified here and here.

[m4rch3n1ng]

i realized that my first attempt didn't properly parse empty use<> bounds, and then i forgot that type identifiers are also allowed, but now it should work properly i think.

theoretically speaking this syntax also allows const generic parameters, but i couldn't find a way to disambiguate between these two, so i just left those to be parsed as type_parameter. while it's impossible to disambiguate a use<N, T> and figure out if N is a type or a const parameter, it should be possible to take a good guess for something like use<LEN, Type>, but i don't know how to do that. (apparently that is already actually something that editors do in their own highlights.scm queries.)

[m4rch3n1ng]

one (hopefully) last quick comment: the reference calls this both precise captures and UseBounds. i initially chose the first one because that was how it was announced, but i think the latter name makes more sense. should i change it? or should i leave it as precise_capture?

[maxbrunsfeld]

I agree with you that use_bounds makes more sense.

[m4rch3n1ng]

changed the name to use_bounds and rebased.

[m4rch3n1ng]

rebased on master again and fixed one of the tests that i added here cause that used a type parameter