I wrote my first custom derive macro

[Yandros]

See:

Proc macros - using third party crate

The Rust solution to this, more general than just to procedural macros, are public dependencies through public reexports: //! Your `lib.rs` // 2018 edition pub use ::itertools; // old style pub extern crate itertools; and then within a macro_rules! macro, for instance, you expand to a path referring to your crate first, which must contain the itertools crate as the second element of the path / as if it were a top-level module: macro_rules! my_izip {( $($input:tt)* ) => ( $crate // …

for a description of the frontend (with traits, re-exporting proc-macro, …) + backend (proc-macro only) crates pattern.

If the frontend crate (say, heapsize, or space_age) happens to call the proc-macro itself, you can put extern crate self as space_age; at the root of its lib.rs to allow referring to your own crate as if it were an external one, making the proc-macro thus usable internally