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// Issue #26656: Verify that trait objects cannot bypass dropck.
// Using this instead of Fn etc. to take HRTB out of the equation.
trait Trigger<B> { fn fire(&self, b: &mut B); }
impl<B: Button> Trigger<B> for () {
fn fire(&self, b: &mut B) {
b.push();
}
}
// Still unsound Zook
trait Button { fn push(&self); }
struct Zook<B> { button: B, trigger: Box<dyn Trigger<B>+'static> }
impl<B> Drop for Zook<B> {
fn drop(&mut self) {
self.trigger.fire(&mut self.button);
}
}
// AND
struct Bomb { usable: bool }
impl Drop for Bomb { fn drop(&mut self) { self.usable = false; } }
impl Bomb { fn activate(&self) { assert!(self.usable) } }
enum B<'a> { HarmlessButton, BigRedButton(&'a Bomb) }
impl<'a> Button for B<'a> {
fn push(&self) {
if let B::BigRedButton(borrowed) = *self {
borrowed.activate();
}
}
}
fn main() {
let (mut zook, ticking);
zook = Zook { button: B::HarmlessButton,
trigger: Box::new(()) };
ticking = Bomb { usable: true };
zook.button = B::BigRedButton(&ticking);
}
//~^^ ERROR `ticking` does not live long enough
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