rust/tests/ui/consts/promoted-const-drop.rs

#![feature(const_trait_impl)]

struct A();

impl const Drop for A {
    fn drop(&mut self) {}
}

const C: A = A();

fn main() {
    let _: &'static A = &A(); //~ ERROR temporary value dropped while borrowed
    let _: &'static [A] = &[C]; //~ ERROR temporary value dropped while borrowed
}
Do not promote values with const drop that need to be dropped Changes from #88558 allowed using `~const Drop` in constants by introducing a new `NeedsNonConstDrop` qualif. The new qualif was also used for promotion purposes, and allowed promotion to happen for values that needs to be dropped but which do have a const drop impl. Since for promoted the drop implementation is never executed, this lead to observable change in behaviour. For example: ```rust struct Panic(); impl const Drop for Panic { fn drop(&mut self) { panic!(); } } fn main() { let _ = &Panic(); } ``` Restore the use of `NeedsDrop` qualif during promotion to avoid the issue. 2021-10-17 00:00:00 +00:00			`#![feature(const_trait_impl)]`

			`struct A();`

			`impl const Drop for A {`
			`fn drop(&mut self) {}`
			`}`

			`const C: A = A();`

			`fn main() {`
			`let _: &'static A = &A(); //~ ERROR temporary value dropped while borrowed`
			`let _: &'static [A] = &[C]; //~ ERROR temporary value dropped while borrowed`
			`}`