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//@ revisions: current next
//@ ignore-compare-mode-next-solver (explicit revisions)
//@[next] compile-flags: -Znext-solver
// We previously wrongly instantiated binders during trait upcasting,
// allowing the super trait to be more generic than the sub trait.
// This was unsound.
#![feature(trait_upcasting)]
trait Supertrait<'a, 'b> {
fn cast(&self, x: &'a str) -> &'b str;
}
trait Subtrait<'a, 'b>: Supertrait<'a, 'b> {}
impl<'a> Supertrait<'a, 'a> for () {
fn cast(&self, x: &'a str) -> &'a str {
x
}
}
impl<'a> Subtrait<'a, 'a> for () {}
fn unsound(x: &dyn for<'a> Subtrait<'a, 'a>) -> &dyn for<'a, 'b> Supertrait<'a, 'b> {
x //~ ERROR mismatched types
//[current]~^ ERROR mismatched types
}
fn transmute<'a, 'b>(x: &'a str) -> &'b str {
unsound(&()).cast(x)
}
fn main() {
let x;
{
let mut temp = String::from("hello there");
x = transmute(temp.as_str());
}
println!("{x}");
}
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