When a proc macro fails you get an error at the site where the macro is used, and a stack trace into the proc macro crate. You can even use tools to expand the

When a proc macro fails you get an error at the site where the macro is used, and a stack trace into the proc macro crate. You can even use tools to expand the proc macro to see what went wrong (although those aren't built in, yet). Debugging a proc macro failure is miles and above easier than debugging template errors.