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#![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() {}
|
