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// Reject mixing cyclic structure and Drop when using trait
// objects to hide the cross-references.
//
// (Compare against ui/span/dropck_vec_cycle_checked.rs)
use std::cell::Cell;
use id::Id;
mod s {
use std::sync::atomic::{AtomicUsize, Ordering};
static S_COUNT: AtomicUsize = AtomicUsize::new(0);
pub fn next_count() -> usize {
S_COUNT.fetch_add(1, Ordering::SeqCst) + 1
}
}
mod id {
use s;
#[derive(Debug)]
pub struct Id {
orig_count: usize,
count: usize,
}
impl Id {
pub fn new() -> Id {
let c = s::next_count();
println!("building Id {}", c);
Id { orig_count: c, count: c }
}
pub fn count(&self) -> usize {
println!("Id::count on {} returns {}", self.orig_count, self.count);
self.count
}
}
impl Drop for Id {
fn drop(&mut self) {
println!("dropping Id {}", self.count);
self.count = 0;
}
}
}
trait HasId {
fn count(&self) -> usize;
}
#[derive(Debug)]
struct CheckId<T:HasId> {
v: T
}
#[allow(non_snake_case)]
fn CheckId<T:HasId>(t: T) -> CheckId<T> { CheckId{ v: t } }
impl<T:HasId> Drop for CheckId<T> {
fn drop(&mut self) {
assert!(self.v.count() > 0);
}
}
trait Obj<'a> : HasId {
fn set0(&self, b: &'a Box<dyn Obj<'a>>);
fn set1(&self, b: &'a Box<dyn Obj<'a>>);
}
struct O<'a> {
id: Id,
obj0: CheckId<Cell<Option<&'a Box<dyn Obj<'a>>>>>,
obj1: CheckId<Cell<Option<&'a Box<dyn Obj<'a>>>>>,
}
impl<'a> HasId for O<'a> {
fn count(&self) -> usize { self.id.count() }
}
impl<'a> O<'a> {
fn new() -> Box<O<'a>> {
Box::new(O {
id: Id::new(),
obj0: CheckId(Cell::new(None)),
obj1: CheckId(Cell::new(None)),
})
}
}
impl<'a> HasId for Cell<Option<&'a Box<dyn Obj<'a>>>> {
fn count(&self) -> usize {
match self.get() {
None => 1,
Some(c) => c.count(),
}
}
}
impl<'a> Obj<'a> for O<'a> {
fn set0(&self, b: &'a Box<dyn Obj<'a>>) {
self.obj0.v.set(Some(b))
}
fn set1(&self, b: &'a Box<dyn Obj<'a>>) {
self.obj1.v.set(Some(b))
}
}
fn f() {
let (o1, o2, o3): (Box<dyn Obj>, Box<dyn Obj>, Box<dyn Obj>) = (O::new(), O::new(), O::new());
o1.set0(&o2); //~ ERROR `o2` does not live long enough
o1.set1(&o3); //~ ERROR `o3` does not live long enough
o2.set0(&o2); //~ ERROR `o2` does not live long enough
o2.set1(&o3); //~ ERROR `o3` does not live long enough
o3.set0(&o1); //~ ERROR `o1` does not live long enough
o3.set1(&o2); //~ ERROR `o2` does not live long enough
}
fn main() {
f();
}
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