Enum rustc_middle::ty::ImplOverlapKind

source ·

pub enum ImplOverlapKind {
    Permitted {
        marker: bool,
    },
    Issue33140,
}

Variants§

§

Permitted

Fields

§marker: bool

Whether or not the impl is permitted due to the trait being a #[marker] trait

These impls are always allowed to overlap.

§

Issue33140

These impls are allowed to overlap, but that raises an issue #33140 future-compatibility warning.

Some background: in Rust 1.0, the trait-object types Send + Sync (today’s dyn Send + Sync) and Sync + Send (now dyn Sync + Send) were different.

The widely-used version 0.1.0 of the crate traitobject had accidentally relied that difference, making what reduces to the following set of impls:

trait Trait {}
impl Trait for dyn Send + Sync {}
impl Trait for dyn Sync + Send {}

Obviously, once we made these types be identical, that code causes a coherence error and a fairly big headache for us. However, luckily for us, the trait Trait used in this case is basically a marker trait, and therefore having overlapping impls for it is sound.

To handle this, we basically regard the trait as a marker trait, with an additional future-compatibility warning. To avoid accidentally “stabilizing” this feature, it has the following restrictions:

The trait must indeed be a marker-like trait (i.e., no items), and must be positive impls.
The trait-ref of both impls must be equal.
The trait-ref of both impls must be a trait object type consisting only of marker traits.
Neither of the impls can have any where-clauses.

Once traitobject 0.1.0 is no longer an active concern, this hack can be removed.

Enum rustc_middle::ty::ImplOverlapKind

Variants§

Permitted

Fields

Issue33140

Trait Implementations§

impl Debug for ImplOverlapKind

fn fmt(&self, f: &mut Formatter<'_>) -> Result

impl PartialEq for ImplOverlapKind

fn eq(&self, other: &ImplOverlapKind) -> bool

fn ne(&self, other: &Rhs) -> bool

impl Eq for ImplOverlapKind

impl StructuralPartialEq for ImplOverlapKind

Auto Trait Implementations§

impl DynSend for ImplOverlapKind

impl DynSync for ImplOverlapKind

impl Freeze for ImplOverlapKind

impl RefUnwindSafe for ImplOverlapKind

impl Send for ImplOverlapKind

impl Sync for ImplOverlapKind

impl Unpin for ImplOverlapKind

impl UnwindSafe for ImplOverlapKind

Blanket Implementations§

impl<T> Aligned for T

const ALIGN: Alignment = _

impl<T> Any for Twhere T: 'static + ?Sized,

fn type_id(&self) -> TypeId

impl<T> AnyEq for Twhere T: Any + PartialEq,

fn equals(&self, other: &(dyn Any + 'static)) -> bool

fn as_any(&self) -> &(dyn Any + 'static)

impl<T> Borrow<T> for Twhere T: ?Sized,

fn borrow(&self) -> &T

impl<T> BorrowMut<T> for Twhere T: ?Sized,

fn borrow_mut(&mut self) -> &mut T

impl<T, R> CollectAndApply<T, R> for T

fn collect_and_apply<I, F>(iter: I, f: F) -> Rwhere I: Iterator<Item = T>, F: FnOnce(&[T]) -> R,

type Output = R

impl<Q, K> Equivalent<K> for Qwhere Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

fn equivalent(&self, key: &K) -> bool

impl<Q, K> Equivalent<K> for Qwhere Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

fn equivalent(&self, key: &K) -> bool

impl<Q, K> Equivalent<K> for Qwhere Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

fn equivalent(&self, key: &K) -> bool

impl<T> Filterable for T

fn filterable( self, filter_name: &'static str ) -> RequestFilterDataProvider<T, fn(_: DataRequest<'_>) -> bool>

impl<T> From<T> for T

fn from(t: T) -> T

impl<T> Instrument for T

fn instrument(self, span: Span) -> Instrumented<Self>

fn in_current_span(self) -> Instrumented<Self>

impl<T, U> Into<U> for Twhere U: From<T>,

fn into(self) -> U

impl<P> IntoQueryParam<P> for P

fn into_query_param(self) -> P

impl<T> MaybeResult<T> for T

type Error = !

fn from(_: Result<T, <T as MaybeResult<T>>::Error>) -> T

fn to_result(self) -> Result<T, <T as MaybeResult<T>>::Error>

impl<T> Pointable for T

const ALIGN: usize = _

type Init = T

unsafe fn init(init: <T as Pointable>::Init) -> usize

unsafe fn deref<'a>(ptr: usize) -> &'a T

unsafe fn deref_mut<'a>(ptr: usize) -> &'a mut T

unsafe fn drop(ptr: usize)

impl<T> Same for T

type Output = T

impl<'tcx, T> ToPredicate<'tcx, T> for T

fn to_predicate(self, _tcx: TyCtxt<'tcx>) -> T

impl<T, U> TryFrom<U> for Twhere U: Into<T>,

type Error = Infallible

fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

impl<T, U> TryInto<U> for Twhere U: TryFrom<T>,

type Error = <U as TryFrom<T>>::Error

fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

impl<V, T> VZip<V> for Twhere V: MultiLane<T>,

fn vzip(self) -> V

impl<Tcx, T> Value<Tcx> for Twhere Tcx: DepContext,

default fn from_cycle_error( tcx: Tcx, cycle_error: &CycleError, _guar: ErrorGuaranteed ) -> T

impl<T> WithSubscriber for T

impl<T> Any for T
where T: 'static + ?Sized,

impl<T> AnyEq for T
where T: Any + PartialEq,

impl<T> Borrow<T> for T
where T: ?Sized,

impl<T> BorrowMut<T> for T
where T: ?Sized,

fn collect_and_apply<I, F>(iter: I, f: F) -> R
where I: Iterator<Item = T>, F: FnOnce(&[T]) -> R,

impl<Q, K> Equivalent<K> for Q
where Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

impl<Q, K> Equivalent<K> for Q
where Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

impl<Q, K> Equivalent<K> for Q
where Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

impl<T, U> Into<U> for T
where U: From<T>,

impl<T, U> TryFrom<U> for T
where U: Into<T>,

impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

impl<V, T> VZip<V> for T
where V: MultiLane<T>,

impl<Tcx, T> Value<Tcx> for T
where Tcx: DepContext,

fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>
where S: Into<Dispatch>,

impl<'a, T> Captures<'a> for T
where T: ?Sized,

impl<T> ErasedDestructor for T
where T: 'static,

impl<T> MaybeSendSync for T
where T: Send + Sync,