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// Another example from issue #84660, this time weaponized as a safe transmute: an opaque type in an
// impl header being accepted was used to create unsoundness.
#![feature(type_alias_impl_trait)]
trait Foo {}
impl Foo for () {}
type Bar = impl Foo;
fn _defining_use() -> Bar {}
trait Trait<T, In> {
type Out;
fn convert(i: In) -> Self::Out;
}
impl<In, Out> Trait<Bar, In> for Out {
type Out = Out;
fn convert(_i: In) -> Self::Out {
unreachable!();
}
}
impl<In, Out> Trait<(), In> for Out { //~ ERROR conflicting implementations of trait `Trait<Bar, _>`
type Out = In;
fn convert(i: In) -> Self::Out {
i
}
}
fn transmute<In, Out>(i: In) -> Out {
<Out as Trait<Bar, In>>::convert(i)
}
fn main() {
let d;
{
let x = "Hello World".to_string();
d = transmute::<&String, &String>(&x);
}
println!("{}", d);
}
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