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#![feature(unsize)] | ||
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use std::marker::Unsize; | ||
use std::rc::Rc; | ||
use std::sync::Arc; | ||
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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>; | ||
} | ||
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impl<T: ?Sized> Cast for T {} | ||
pub trait Cast { | ||
fn cast<T: ?Sized>(&self) -> &T | ||
where | ||
Self: CastTo<T>, | ||
{ | ||
self | ||
} | ||
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fn cast_mut<T>(&mut self) -> &mut T | ||
where | ||
Self: CastTo<T>, | ||
{ | ||
self.cast_mut_to() | ||
} | ||
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fn into_cast<T>(self: Box<Self>) -> Box<T> | ||
where | ||
Self: CastTo<T>, | ||
{ | ||
self.into_cast_to() | ||
} | ||
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fn cast_rc<T>(self: Rc<Self>) -> Rc<T> | ||
where | ||
Self: CastTo<T>, | ||
{ | ||
self.cast_rc_to() | ||
} | ||
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fn cast_arc<T>(self: Arc<Self>) -> Arc<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 | ||
} | ||
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fn cast_mut_to(&mut self) -> &mut T { | ||
self | ||
} | ||
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fn into_cast_to(self: Box<Self>) -> Box<T> { | ||
self | ||
} | ||
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fn cast_rc_to(self: Rc<Self>) -> Rc<T> { | ||
self | ||
} | ||
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fn cast_arc_to(self: Arc<Self>) -> Arc<T> { | ||
self | ||
} | ||
} | ||
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pub trait Foo { | ||
fn foo(&self) { | ||
println!("Foo({})", core::any::type_name::<Self>()); | ||
} | ||
} | ||
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pub trait Bar: CastTo<dyn Foo> + CastTo<dyn core::fmt::Debug> + CastTo<[i32]> { | ||
fn bar(&self) { | ||
println!("Bar({})", core::any::type_name::<Self>()); | ||
} | ||
} | ||
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impl Foo for [i32; 10] {} | ||
impl Bar for [i32; 10] {} | ||
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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 | ||
} |
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error[E0277]: the trait bound `dyn Bar: CastTo<[i32]>` is not satisfied | ||
--> $DIR/issue-71659.rs:92:18 | ||
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LL | let x = (*x).cast::<[i32]>(); | ||
| ^^^^ the trait `CastTo<[i32]>` is not implemented for `dyn Bar` | ||
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error: aborting due to previous error | ||
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For more information about this error, try `rustc --explain E0277`. |