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33 lines
579 B
Rust
33 lines
579 B
Rust
#![feature(unsize)]
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use std::marker::Unsize;
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pub trait CastTo<T: ?Sized>: Unsize<T> {
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fn cast_to(&self) -> &T;
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}
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impl<T: ?Sized, U: ?Sized + Unsize<T>> CastTo<T> for U {
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fn cast_to(&self) -> &T {
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self
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}
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}
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impl<T: ?Sized> Cast for T {}
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pub trait Cast {
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fn cast<T: ?Sized>(&self) -> &T
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where
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Self: CastTo<T>,
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{
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self
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}
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}
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pub trait Foo: CastTo<[i32]> {}
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impl Foo for [i32; 0] {}
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fn main() {
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let x: &dyn Foo = &[];
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let x = x.cast::<[i32]>();
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//~^ ERROR: the trait bound `dyn Foo: CastTo<[i32]>` is not satisfied
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}
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