Using $crate in Rust's procedural macros?

Question

I know what the $crate variable is, but as far as I can tell, it can\'t be used inside procedural macros. Is there another way to achieve a similar effect?

I have an ex

Answer 1

In Edition 2015 (classic Rust), you can do this (but it's hacky):

• use ::defining_crate::SomeTrait in the macro
• within third-party crates depending on defining_crate, the above works fine

• within defining_crate itself, add a module in the root:

  mod defining_crate { pub use super::*; }

In Edition 2018 even more hacky solutions are required (see this issue), though #55275 may give us a simple workaround.