Use smaller example for issue-71659

Author: JohnTitor

src/test/ui/unsized/issue-71659.rs

@@ -1,94 +1,32 @@
 #![feature(unsize)]
 
 use std::marker::Unsize;
-use std::rc::Rc;
-use std::sync::Arc;
 
 pub trait CastTo<T: ?Sized>: Unsize<T> {
  fn cast_to(&self) -> &T;
- fn cast_mut_to(&mut self) -> &mut T;
- fn into_cast_to(self: Box<Self>) -> Box<T>;
- fn cast_rc_to(self: Rc<Self>) -> Rc<T>;
- fn cast_arc_to(self: Arc<Self>) -> Arc<T>;
 }
 
-impl<T: ?Sized> Cast for T {}
-pub trait Cast {
- fn cast<T: ?Sized>(&self) -> &T
- where
- Self: CastTo<T>,
- {
+impl<T: ?Sized, U: ?Sized + Unsize<T>> CastTo<T> for U {
+ fn cast_to(&self) -> &T {
  self
  }
+}
 
- fn cast_mut<T>(&mut self) -> &mut T
- where
- Self: CastTo<T>,
- {
- self.cast_mut_to()
- }
-
- fn into_cast<T>(self: Box<Self>) -> Box<T>
- where
- Self: CastTo<T>,
- {
- self.into_cast_to()
- }
-
- fn cast_rc<T>(self: Rc<Self>) -> Rc<T>
- where
- Self: CastTo<T>,
- {
- self.cast_rc_to()
- }
-
- fn cast_arc<T>(self: Arc<Self>) -> Arc<T>
+impl<T: ?Sized> Cast for T {}
+pub trait Cast {
+ fn cast<T: ?Sized>(&self) -> &T
  where
  Self: CastTo<T>,
  {
- self.cast_arc_to()
- }
-}
-impl<T: ?Sized, U: ?Sized + Unsize<T>> CastTo<T> for U {
- fn cast_to(&self) -> &T {
- self
- }
-
- fn cast_mut_to(&mut self) -> &mut T {
- self
- }
-
- fn into_cast_to(self: Box<Self>) -> Box<T> {
  self
  }
-
- fn cast_rc_to(self: Rc<Self>) -> Rc<T> {
- self
- }
-
- fn cast_arc_to(self: Arc<Self>) -> Arc<T> {
- self
- }
-}
-
-pub trait Foo {
- fn foo(&self) {
- println!("Foo({})", core::any::type_name::<Self>());
- }
-}
-
-pub trait Bar: CastTo<dyn Foo> + CastTo<dyn core::fmt::Debug> + CastTo<[i32]> {
- fn bar(&self) {
- println!("Bar({})", core::any::type_name::<Self>());
- }
 }
 
-impl Foo for [i32; 10] {}
-impl Bar for [i32; 10] {}
+pub trait Foo: CastTo<[i32]> {}
+impl Foo for [i32; 0] {}
 
 fn main() {
- let x = [0; 10];
- let x: Box<dyn Bar> = Box::new(x);
- let x = (*x).cast::<[i32]>();
- //~^ ERROR: the trait bound `dyn Bar: CastTo<[i32]>` is not satisfied
+ let x: &dyn Foo = &[];
+ let x = x.cast::<[i32]>();
+ //~^ ERROR: the trait bound `dyn Foo: CastTo<[i32]>` is not satisfied
 }

src/test/ui/unsized/issue-71659.stderr

@@ -1,8 +1,8 @@
-error[E0277]: the trait bound `dyn Bar: CastTo<[i32]>` is not satisfied
- --> $DIR/issue-71659.rs:92:18
+error[E0277]: the trait bound `dyn Foo: CastTo<[i32]>` is not satisfied
+ --> $DIR/issue-71659.rs:30:15
  |
-LL | let x = (*x).cast::<[i32]>();
- |  ^^^^ the trait `CastTo<[i32]>` is not implemented for `dyn Bar`
+LL | let x = x.cast::<[i32]>();
+ | ^^^^ the trait `CastTo<[i32]>` is not implemented for `dyn Foo`
 
 error: aborting due to previous error