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// Check that a self parameter type requires a DispatchFromDyn impl to be dyn-compatible.
#![feature(arbitrary_self_types, unsize, coerce_unsized)]
use std::{
marker::Unsize,
ops::{CoerceUnsized, Deref},
};
struct Ptr<T: ?Sized>(Box<T>);
impl<T: ?Sized> Deref for Ptr<T> {
type Target = T;
fn deref(&self) -> &T {
&*self.0
}
}
impl<T: Unsize<U> + ?Sized, U: ?Sized> CoerceUnsized<Ptr<U>> for Ptr<T> {}
// Because this impl is missing the coercion below fails.
// impl<T: Unsize<U> + ?Sized, U: ?Sized> DispatchFromDyn<Ptr<U>> for Ptr<T> {}
trait Trait {
fn ptr(self: Ptr<Self>);
}
impl Trait for i32 {
fn ptr(self: Ptr<Self>) {}
}
fn main() {
Ptr(Box::new(4)) as Ptr<dyn Trait>;
//~^ ERROR the trait `Trait` cannot be made into an object
//~^^ ERROR the trait `Trait` cannot be made into an object
}
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