mirror of https://github.com/rust-lang/rust
57 lines
1.3 KiB
Rust
57 lines
1.3 KiB
Rust
//@ check-pass
|
|
//@ revisions: old next
|
|
//@[next] compile-flags: -Znext-solver
|
|
|
|
#![feature(ptr_metadata)]
|
|
|
|
use std::ptr::{self, Pointee};
|
|
|
|
fn cast_same_meta<T: ?Sized, U: ?Sized>(ptr: *const T) -> *const U
|
|
where
|
|
T: Pointee<Metadata = <U as Pointee>::Metadata>,
|
|
{
|
|
let (thin, meta) = ptr.to_raw_parts();
|
|
ptr::from_raw_parts(thin, meta)
|
|
}
|
|
|
|
struct Wrapper<T: ?Sized>(T);
|
|
|
|
// normalize `Wrapper<T>::Metadata` -> `T::Metadata`
|
|
fn wrapper_to_tail<T: ?Sized>(ptr: *const T) -> *const Wrapper<T> {
|
|
cast_same_meta(ptr)
|
|
}
|
|
|
|
// normalize `Wrapper<T>::Metadata` -> `T::Metadata` -> `()`
|
|
fn wrapper_to_unit<T>(ptr: *const ()) -> *const Wrapper<T> {
|
|
cast_same_meta(ptr)
|
|
}
|
|
|
|
trait Project {
|
|
type Assoc: ?Sized;
|
|
}
|
|
|
|
struct WrapperProject<T: ?Sized + Project>(T::Assoc);
|
|
|
|
// normalize `WrapperProject<T>::Metadata` -> `T::Assoc::Metadata`
|
|
fn wrapper_project_tail<T: ?Sized + Project>(ptr: *const T::Assoc) -> *const WrapperProject<T> {
|
|
cast_same_meta(ptr)
|
|
}
|
|
|
|
// normalize `WrapperProject<T>::Metadata` -> `T::Assoc::Metadata` -> `()`
|
|
fn wrapper_project_unit<T: ?Sized + Project>(ptr: *const ()) -> *const WrapperProject<T>
|
|
where
|
|
T::Assoc: Sized,
|
|
{
|
|
cast_same_meta(ptr)
|
|
}
|
|
|
|
// normalize `<[T] as Pointee>::Metadata` -> `usize`, even if `[T]: Sized`
|
|
fn sized_slice<T>(ptr: *const [T]) -> *const str
|
|
where
|
|
[T]: Sized,
|
|
{
|
|
cast_same_meta(ptr)
|
|
}
|
|
|
|
fn main() {}
|