I think that would be worth doing, but more than the backward compat problem, the main complication I see would be in the syntax/grammar/macro expansion. Like,

I think that would be worth doing, but more than the backward compat problem, the main complication I see would be in the syntax/grammar/macro expansion. Like, say we wanted to make cxx or autocxx macros unsafe. We'd need to allow at item scope writing this: mod foo { unsafe { my_unsafe_macro!() } } and we'd "somehow" have to check that unsafe macros are only expanded within unsafe "scopes", rejecting the program otherwise (can't be a type error because we can't do type checking before macro expansion). Also, these unsafe scopes would need to export all the items, etc. I don't know. Seems like a lot of contortion for something that could be solved with just a rename like other have proposed, e.g., unsafe_autocxx_include!(...); Might be worth opening an internal threads about this. Maybe Centril could shed more like on how hard this would actually be. Most (all?) macros that I regularly use are sound (the derives, println!, debug!, offset_of!, pin_mut!...). So it might also be worth looking into how common of a problem this is. I've seen soundness bugs in macros before (offset_of!), but these were always bugs. This is the first time I recall a macro that's unsound by design.