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