[binarybanana]

You can add descriptive error messages when an error happens (like multiple mutable borrows) during macro expansion. Macros are just regular list code, so all runtime features like printing functions are available.

You could even write a FPS using OpenGL where shooting functions, or pieces of suctions removes them from the current compile job (or even deletes them from the source code entirely). In a macro.

[tialaramex]

I mean, that's nice, Rust's proc macros get to emit descriptive error messages† too, but for that to happen the macro expansion occurred and that means we didn't have a parse error. So you're dodging the problem.

† Or of course, to deliberately not emit descriptive error messages, e.g. whichever-compiles!