bevy/docs/debugging.md

Debugging

Macro Debugging

• Print the final output of a macro using cargo rustc --profile=check -- -Zunstable-options --pretty=expanded
  • Alternatively you could install and use cargo expand which adds syntax highlighting to the terminal output.
    • Additionally get pager by piping to less ( on Unix systems ): cargo expand --color always | less -R
• Print output during macro compilation using eprintln!("hi");