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#![feature(coroutines)]
#![feature(coroutine_clone)]
#![feature(coroutine_trait)]
#![feature(rustc_attrs, stmt_expr_attributes)]
use std::ops::Coroutine;
use std::pin::Pin;
fn copy<T: Copy>(x: T) -> T {
x
}
fn main() {
let mut g = || {
// This is desuraged as 4 stages:
// - allocate a `*mut u8` with `exchange_malloc`;
// - create a Box that is ignored for trait computations;
// - compute fields (and yields);
// - assign to `t`.
let t = #[rustc_box]
Box::new((5, yield));
drop(t);
};
// Allocate the temporary box.
Pin::new(&mut g).resume(());
// The temporary box is in coroutine locals.
// As it is not taken into account for trait computation,
// the coroutine is `Copy`.
let mut h = copy(g);
//~^ ERROR the trait bound `Box<(i32, ())>: Copy` is not satisfied in
// We now have 2 boxes with the same backing allocation:
// one inside `g` and one inside `h`.
// Proceed and drop `t` in `g`.
Pin::new(&mut g).resume(());
//~^ ERROR borrow of moved value: `g`
// Proceed and drop `t` in `h` -> double free!
Pin::new(&mut h).resume(());
}
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