heapsize_derive is a procedural macro. It will run at compile time and transform your program's source code.
Adding heapsize_derive macro(s) as a dependency
Run this command in a terminal, in your project's directory:
cargo add heapsize_derive
To add it manually, edit your project's Cargo.toml file and add to the [dependencies] section:
heapsize_derive = "0.1.4"
You may need to import the macro(s) with use heapsize_derive::*.
heapsize_derive documentation.