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|
#![feature(arbitrary_self_types, coerce_unsized, dispatch_from_dyn, unsize)]
#![feature(unsized_locals, unsized_fn_params)]
//~^ WARN the feature `unsized_locals` is incomplete
// This tests a few edge-cases around `arbitrary_self_types`. Most specifically,
// it checks that the `ObjectCandidate` you get from method matching can't
// match a trait with the same DefId as a supertrait but a bad type parameter.
use std::marker::PhantomData;
mod internal {
use std::ops::{CoerceUnsized, Deref, DispatchFromDyn};
use std::marker::{PhantomData, Unsize};
pub struct Smaht<T: ?Sized, MISC>(pub Box<T>, pub PhantomData<MISC>);
impl<T: ?Sized, MISC> Deref for Smaht<T, MISC> {
type Target = T;
fn deref(&self) -> &Self::Target {
&self.0
}
}
impl<T: ?Sized + Unsize<U>, U: ?Sized, MISC> CoerceUnsized<Smaht<U, MISC>>
for Smaht<T, MISC>
{}
impl<T: ?Sized + Unsize<U>, U: ?Sized, MISC> DispatchFromDyn<Smaht<U, MISC>>
for Smaht<T, MISC>
{}
pub trait Foo: X<u32> {}
pub trait X<T> {
fn foo(self: Smaht<Self, T>) -> T;
}
impl X<u32> for () {
fn foo(self: Smaht<Self, u32>) -> u32 {
0
}
}
pub trait Marker {}
impl Marker for dyn Foo {}
impl<T: Marker + ?Sized> X<u64> for T {
fn foo(self: Smaht<Self, u64>) -> u64 {
1
}
}
impl Deref for dyn Foo {
type Target = ();
fn deref(&self) -> &() { &() }
}
impl Foo for () {}
}
pub trait FinalFoo {
fn foo(&self) -> u8;
}
impl FinalFoo for () {
fn foo(&self) -> u8 { 0 }
}
mod nuisance_foo {
pub trait NuisanceFoo {
fn foo(self);
}
impl<T: ?Sized> NuisanceFoo for T {
fn foo(self) {}
}
}
fn objectcandidate_impl() {
let x: internal::Smaht<(), u32> = internal::Smaht(Box::new(()), PhantomData);
let x: internal::Smaht<dyn internal::Foo, u32> = x;
// This picks `<dyn internal::Foo as X<u32>>::foo` via `ObjectCandidate`.
//
// The `TraitCandidate` is not relevant because `X` is not in scope.
let z = x.foo();
// Observe the type of `z` is `u32`
let _seetype: () = z; //~ ERROR mismatched types
//~| expected `()`, found `u32`
}
fn traitcandidate_impl() {
use internal::X;
let x: internal::Smaht<(), u64> = internal::Smaht(Box::new(()), PhantomData);
let x: internal::Smaht<dyn internal::Foo, u64> = x;
// This picks `<dyn internal::Foo as X<u64>>::foo` via `TraitCandidate`.
//
// The `ObjectCandidate` does not apply, as it only applies to
// `X<u32>` (and not `X<u64>`).
let z = x.foo();
// Observe the type of `z` is `u64`
let _seetype: () = z; //~ ERROR mismatched types
//~| expected `()`, found `u64`
}
fn traitcandidate_impl_with_nuisance() {
use internal::X;
use nuisance_foo::NuisanceFoo;
let x: internal::Smaht<(), u64> = internal::Smaht(Box::new(()), PhantomData);
let x: internal::Smaht<dyn internal::Foo, u64> = x;
// This picks `<dyn internal::Foo as X<u64>>::foo` via `TraitCandidate`.
//
// The `ObjectCandidate` does not apply, as it only applies to
// `X<u32>` (and not `X<u64>`).
//
// The NuisanceFoo impl has the same priority as the `X` impl,
// so we get a conflict.
let z = x.foo(); //~ ERROR multiple applicable items in scope
}
fn neither_impl() {
let x: internal::Smaht<(), u64> = internal::Smaht(Box::new(()), PhantomData);
let x: internal::Smaht<dyn internal::Foo, u64> = x;
// This can't pick the `TraitCandidate` impl, because `Foo` is not
// imported. However, this also can't pick the `ObjectCandidate`
// impl, because it only applies to `X<u32>` (and not `X<u64>`).
//
// Therefore, neither of the candidates is applicable, and we pick
// the `FinalFoo` impl after another deref, which will return `u8`.
let z = x.foo();
// Observe the type of `z` is `u8`
let _seetype: () = z; //~ ERROR mismatched types
//~| expected `()`, found `u8`
}
fn both_impls() {
use internal::X;
let x: internal::Smaht<(), u32> = internal::Smaht(Box::new(()), PhantomData);
let x: internal::Smaht<dyn internal::Foo, u32> = x;
// This can pick both the `TraitCandidate` and the `ObjectCandidate` impl.
//
// However, the `ObjectCandidate` is considered an "inherent candidate",
// and therefore has priority over both the `TraitCandidate` as well as
// any other "nuisance" candidate" (if present).
let z = x.foo();
// Observe the type of `z` is `u32`
let _seetype: () = z; //~ ERROR mismatched types
//~| expected `()`, found `u32`
}
fn both_impls_with_nuisance() {
// Similar to the `both_impls` example, except with a nuisance impl to
// make sure the `ObjectCandidate` indeed has a higher priority.
use internal::X;
use nuisance_foo::NuisanceFoo;
let x: internal::Smaht<(), u32> = internal::Smaht(Box::new(()), PhantomData);
let x: internal::Smaht<dyn internal::Foo, u32> = x;
let z = x.foo();
// Observe the type of `z` is `u32`
let _seetype: () = z; //~ ERROR mismatched types
//~| expected `()`, found `u32`
}
fn main() {
}
|
