rust/tests/ui/nll/issue-27282-mutate-before-diverging-arm-1.rs
2023-01-11 09:32:08 +00:00

32 lines
1.1 KiB
Rust

// This is testing an attempt to corrupt the discriminant of the match
// arm in a guard, followed by an attempt to continue matching on that
// corrupted discriminant in the remaining match arms.
//
// Basically this is testing that our new NLL feature of emitting a
// fake read on each match arm is catching cases like this.
//
// This case is interesting because it includes a guard that
// diverges, and therefore a single final fake-read at the very end
// after the final match arm would not suffice.
struct ForceFnOnce;
fn main() {
let mut x = &mut Some(&2);
let force_fn_once = ForceFnOnce;
match x {
&mut None => panic!("unreachable"),
&mut Some(&_) if {
// ForceFnOnce needed to exploit #27282
(|| { *x = None; drop(force_fn_once); })();
//~^ ERROR cannot mutably borrow `x` in match guard [E0510]
false
} => {}
&mut Some(&a) if { // this binds to garbage if we've corrupted discriminant
println!("{}", a);
panic!()
} => {}
_ => panic!("unreachable"),
}
}