Declarative macro repetition counts about lang-team

[nikomatsakis]

No update this week.

[markbt]

Project update

I've started looking at expanding more on the idea of general-purpose metavariable expressions (${ ... }) for use in extending the macro language, where macro repetition counts are the first user. It's coming together pretty nicely.

For a real-world example, this line in one of my crates would become:

let size = ${count(value)};

There is a prototype implementation on the markbt/rust:metavariable_expressions branch. If you'd like to try it out, any feedback would be welcome.

I've started drafting an RFC on the markbt/lang-team:metavar_expr_rfc branch (Rendered). It's still in its early stages, but feedback and contributions are always welcome.

Cc: @Lokathor @rust-lang/lang

[nikomatsakis]

Project update

• rust-lang/rfcs#3086 is posted!

[nikomatsakis]

Closing this in favor of rust-lang/rust#83527