Rust code highlighting fixes

[HarryLovesCode]

Fixes incorrect highlighting of:

• String escapes
• Feature gates, attributes
• Underscores in numbers

[jneen]

should shebangs have to be at the beginning (\A) of the file?

[jneen]

Hi @HarryLovesCode, could you add some code to spec/visual/samples/rust that exercises these fixes and make sure it looks right (by running bundle exec rackup and visiting localhost:9292/rust)

[HarryLovesCode]

Tell me if this needs to be squashed or if there are any concerns you have.

[jneen]

This file is far too long to be a demo now. It is not important to me that the demos compile correctly, just that they show off a little bit of the highlighting. Is there a smaller snippet you could provide here?

[jneen]

Hi @HarryLovesCode, I think you added your example to the wrong file - lib/rouge/demos/rust is a little taste of what highlighted rust code looks like. I want you to add an example to spec/visual/samples/rust, which stress-tests all the little features and corner cases.

[hugopeixoto]

Most of the issues addressed by this PR have already been merged:

• attributes
• string escapes
• underscores in integers
• division operator

I opened two PRs with the missing features:

• tuple indexing (Bugfix: Allow rust tuple indexing #1580)
• underscores in floats (Bugfix: support rust float delimiters #1581)

[pyrmont]

@HarryLovesCode I'm really sorry it took so long to get this all squared away but I've just merged in the two PRs @hugopeixoto opened for the outstanding issues and they'll be part of the next release of Rouge, v3.23.0. That's actually due to come out later today/early tomorrow (depending on your time zone). Given it's been four (!) years, I don't blame you if you've moved on but wanted to keep you in the loop just in case!

@hugopeixoto Thanks so much for both submitting the remaining PRs and doing the yeoman's work of actually tracking down the PRs where the changes had been subsequently added. Really appreciate it!