Zig got too much in to avoiding "hidden behavior" that destructors and operator overloading were banned. Operator overloading is indeed a mess, but destructors are too useful. The only compromise for destructors was adding the "defer" feature. (Was there ever a corresponding "error if you don't defer" feature?)
No, defer is always optional, which makes it highly error prone.
There's errdefer, which only defers if there was an error, but presumably you meant what you wrote, and not that.
BTW, D was the first language to have defer, invented by Andrei Alexandrescu who urged Walter Bright to add it to D 2.0 ... in D it's spelled scope(exit) = defer, scope(failure) = errdefer, and scope(success) which is only run if no error.
