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// Test to ensure that trait bounds are propertly
// checked on specializable associated types
#![allow(incomplete_features)]
#![feature(specialization)]
trait UncheckedCopy: Sized {
type Output: From<Self> + Copy + Into<Self>;
}
impl<T> UncheckedCopy for T {
default type Output = Self;
//~^ ERROR: the trait bound `T: Copy` is not satisfied
}
fn unchecked_copy<T: UncheckedCopy>(other: &T::Output) -> T {
(*other).into()
}
fn bug(origin: String) {
// Turn the String into it's Output type...
// Which we can just do by `.into()`, the assoc type states `From<Self>`.
let origin_output = origin.into();
// Make a copy of String::Output, which is a String...
let mut copy: String = unchecked_copy::<String>(&origin_output);
// Turn the Output type into a String again,
// Which we can just do by `.into()`, the assoc type states `Into<Self>`.
let mut origin: String = origin_output.into();
// assert both Strings use the same buffer.
assert_eq!(copy.as_ptr(), origin.as_ptr());
// Any use of the copy we made becomes invalid,
drop(origin);
// OH NO! UB UB UB UB!
copy.push_str(" world!");
println!("{}", copy);
}
fn main() {
bug(String::from("hello"));
}
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