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