rust/tests/ui/traits/vtable/impossible-method.rs

39 lines
806 B
Rust

//@ run-pass
//@ revisions: current next
//@ ignore-compare-mode-next-solver (explicit revisions)
//@[next] compile-flags: -Znext-solver
trait Id {
type This<'a>;
}
impl<T> Id for T {
type This<'a> = T;
}
trait Trait<T> {}
impl<T: Id> Trait<for<'a> fn(T::This<'a>)> for T {}
trait Method<T: Id> {
fn call_me(&self)
where
T: Trait<for<'a> fn(T::This<'a>)>;
}
impl<T, U> Method<U> for T {
fn call_me(&self) {
println!("method was reachable");
}
}
fn generic<T: Id>(x: &dyn Method<T>) {
// Proving `T: Trait<for<'a> fn(T::This<'a>)>` holds.
x.call_me();
}
fn main() {
// Proving `u32: Trait<fn(u32)>` fails due to incompleteness.
// We don't add the method to the vtable of `dyn Method`, so
// calling it causes UB.
generic::<u32>(&());
}