Reading Club: Continuing Declarative (macro_rules!) macro improvements

• April 15 2025
• Participant: Vincent (@vincenzopalazzo), Josh (@joshtriplett)

Topic

Reading club about the rust project goal 2025

• Project Goals: https://rust-lang.github.io/rust-project-goals/2025h1/macro-improvements.html
• Project Goal: https://github.com/rust-lang/rust-project-goals/issues/252

Reading the RFC https://github.com/joshtriplett/rfcs/blob/declarative-attribute-macros.md/text/3697-declarative-attribute-macros.md

Minutes

Discussion about priorities for prototyping order:

• Attribute macros
• Derive macros
• Initial macro fragment fields
• Further

Questions

Vincent: Wondering if writing the attr macro in the following way is more intuitive for the user & make the code to implement from the compiler side easy and reusable

macro_rules! main {
    attr { 
        ($func:item) => { make_async_main!($func) };
        (threads = $threads:literal) ($func:item) => { make_async_main!($threads, $func) };
    }
}