Help stabilize a subset of Macros 2.0!

language design
67

Some more sleuthing:

  • RFC 1561 (macro naming and modularization) seems to suggest that use should work on declarative macros 2.0.
  • Talk in the tracking issue also seems to take this as a given. I.e. it is only macro_rules! macros that should get the short end of the stick.
  • The “roadmap” for that issue has every box ticked with no explicit mention of decl macros 2.0.
  • declarative macros 2.0 still has no documentation

Baaaahhhhhh, you know what? Documentation or no documentation, I’m just going to copy the first thing I see on the tracking issue, tweak it until it compiles, and see what happens:

#![feature(decl_macro)]

fn main() {
  println!("{}", m::m_helper!());
}

mod m {
  pub macro m_helper() {
    3
  }
}

Output:

3

Whew! So there you have it. Contrary to what I previously said, it appears that use-able, locally-defined macros are not only planned, but they are already implemented (at least partially). However, it is only for declarative macros 2.0 (macro, not macro_rules!)

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