mirror of https://github.com/rust-lang/rust
56 lines
1.3 KiB
Rust
56 lines
1.3 KiB
Rust
#![allow(unreachable_code)]
|
|
|
|
use std::marker::PhantomData;
|
|
use std::ops::Deref;
|
|
use std::sync::Arc;
|
|
|
|
pub struct Guard<T> {
|
|
_phantom: PhantomData<T>,
|
|
}
|
|
impl<T> Deref for Guard<T> {
|
|
type Target = T;
|
|
fn deref(&self) -> &T {
|
|
unimplemented!()
|
|
}
|
|
}
|
|
|
|
pub struct DirectDeref<T>(T);
|
|
impl<T> Deref for DirectDeref<Arc<T>> {
|
|
type Target = T;
|
|
fn deref(&self) -> &T {
|
|
unimplemented!()
|
|
}
|
|
}
|
|
|
|
pub trait Access<T> {
|
|
type Guard: Deref<Target = T>;
|
|
fn load(&self) -> Self::Guard {
|
|
unimplemented!()
|
|
}
|
|
}
|
|
impl<T, A: Access<T>, P: Deref<Target = A>> Access<T> for P {
|
|
//~^ NOTE: required for `Arc<ArcSwapAny<Arc<usize>>>` to implement `Access<_>`
|
|
//~| NOTE unsatisfied trait bound introduced here
|
|
type Guard = A::Guard;
|
|
}
|
|
impl<T> Access<T> for ArcSwapAny<T> {
|
|
//~^ NOTE: multiple `impl`s satisfying `ArcSwapAny<Arc<usize>>: Access<_>` found
|
|
type Guard = Guard<T>;
|
|
}
|
|
impl<T> Access<T> for ArcSwapAny<Arc<T>> {
|
|
type Guard = DirectDeref<Arc<T>>;
|
|
}
|
|
|
|
pub struct ArcSwapAny<T> {
|
|
_phantom_arc: PhantomData<T>,
|
|
}
|
|
|
|
pub fn foo() {
|
|
let s: Arc<ArcSwapAny<Arc<usize>>> = unimplemented!();
|
|
let guard: Guard<Arc<usize>> = s.load();
|
|
//~^ ERROR: type annotations needed
|
|
//~| HELP: try using a fully qualified path to specify the expected types
|
|
}
|
|
|
|
fn main() {}
|