Trait rustc_data_structures::sync::Sync

1.0.0 · source ·
pub unsafe auto trait Sync { }
Expand description

Types for which it is safe to share references between threads.

This trait is automatically implemented when the compiler determines it’s appropriate.

The precise definition is: a type T is Sync if and only if &T is Send. In other words, if there is no possibility of undefined behavior (including data races) when passing &T references between threads.

As one would expect, primitive types like u8 and f64 are all Sync, and so are simple aggregate types containing them, like tuples, structs and enums. More examples of basic Sync types include “immutable” types like &T, and those with simple inherited mutability, such as Box<T>, Vec<T> and most other collection types. (Generic parameters need to be Sync for their container to be Sync.)

A somewhat surprising consequence of the definition is that &mut T is Sync (if T is Sync) even though it seems like that might provide unsynchronized mutation. The trick is that a mutable reference behind a shared reference (that is, & &mut T) becomes read-only, as if it were a & &T. Hence there is no risk of a data race.

A shorter overview of how Sync and Send relate to referencing:

  • &T is Send if and only if T is Sync
  • &mut T is Send if and only if T is Send
  • &T and &mut T are Sync if and only if T is Sync

Types that are not Sync are those that have “interior mutability” in a non-thread-safe form, such as Cell and RefCell. These types allow for mutation of their contents even through an immutable, shared reference. For example the set method on Cell<T> takes &self, so it requires only a shared reference &Cell<T>. The method performs no synchronization, thus Cell cannot be Sync.

Another example of a non-Sync type is the reference-counting pointer Rc. Given any reference &Rc<T>, you can clone a new Rc<T>, modifying the reference counts in a non-atomic way.

For cases when one does need thread-safe interior mutability, Rust provides atomic data types, as well as explicit locking via sync::Mutex and sync::RwLock. These types ensure that any mutation cannot cause data races, hence the types are Sync. Likewise, sync::Arc provides a thread-safe analogue of Rc.

Any types with interior mutability must also use the cell::UnsafeCell wrapper around the value(s) which can be mutated through a shared reference. Failing to doing this is undefined behavior. For example, transmute-ing from &T to &mut T is invalid.

See the Nomicon for more details about Sync.

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impl !Sync for LocalWaker

1.26.0 · source§

impl !Sync for Args

1.26.0 · source§

impl !Sync for ArgsOs

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impl Sync for OwnedSlice

1.6.0 · source§

impl Sync for alloc::string::Drain<'_>

1.34.0 · source§

impl Sync for AtomicI8

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impl Sync for AtomicI16

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impl Sync for AtomicI32

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impl Sync for AtomicI64

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impl Sync for AtomicIsize

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impl Sync for AtomicU8

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impl Sync for AtomicU16

1.36.0 · source§

impl Sync for Waker

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impl Sync for AtomicBool

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impl Sync for AtomicU32

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impl Sync for AtomicU64

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impl Sync for AtomicUsize

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impl Sync for Collector

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impl Sync for GuardNoSend

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impl Sync for Scope<'_>

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impl Sync for Select<'_>

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impl Sync for Unparker

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impl<'a> Sync for IoSlice<'a>

1.44.0 · source§

impl<'a> Sync for IoSliceMut<'a>

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impl<'a, 'b, K, Q, V, S, A> Sync for hashbrown::map::OccupiedEntryRef<'a, 'b, K, Q, V, S, A>
where K: Sync, Q: Sync + ?Sized, V: Sync, S: Sync, A: Sync + Allocator,

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impl<'a, 'b, K, Q, V, S, A> Sync for OccupiedEntryRef<'a, 'b, K, Q, V, S, A>
where K: Sync, Q: Sync + ?Sized, V: Sync, S: Sync, A: Sync + Allocator,

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impl<'a, R, G, T> Sync for MappedReentrantMutexGuard<'a, R, G, T>
where R: RawMutex + Sync + 'a, G: GetThreadId + Sync + 'a, T: Sync + 'a + ?Sized,

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impl<'a, R, G, T> Sync for ReentrantMutexGuard<'a, R, G, T>
where R: RawMutex + Sync + 'a, G: GetThreadId + Sync + 'a, T: Sync + 'a + ?Sized,

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impl<'a, R, T> Sync for MappedMutexGuard<'a, R, T>
where R: RawMutex + Sync + 'a, T: Sync + 'a + ?Sized,

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impl<'a, R, T> Sync for MappedRwLockReadGuard<'a, R, T>
where R: RawRwLock + 'a, T: Sync + 'a + ?Sized,

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impl<'a, R, T> Sync for MappedRwLockWriteGuard<'a, R, T>
where R: RawRwLock + 'a, T: Sync + 'a + ?Sized,

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impl<'a, R, T> Sync for MutexGuard<'a, R, T>
where R: RawMutex + Sync + 'a, T: Sync + 'a + ?Sized,

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impl<'a, R, T> Sync for RwLockUpgradableReadGuard<'a, R, T>
where R: RawRwLockUpgrade + 'a, T: Sync + 'a + ?Sized,

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impl<'a, T> Sync for smallvec::Drain<'a, T>
where T: Sync + Array,

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impl<'a, T> Sync for OnceRef<'a, T>
where T: Sync,

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impl<'a, T, const CAP: usize> Sync for arrayvec::arrayvec::Drain<'a, T, CAP>
where T: Sync,

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impl<Dyn> Sync for DynMetadata<Dyn>
where Dyn: ?Sized,

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impl<K, V, A> Sync for RustcOccupiedEntry<'_, K, V, A>
where K: Sync, V: Sync, A: Allocator + Sync,

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impl<K, V, S, A> Sync for hashbrown::map::OccupiedEntry<'_, K, V, S, A>
where K: Sync, V: Sync, S: Sync, A: Sync + Allocator,

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impl<K, V, S, A> Sync for hashbrown::map::RawOccupiedEntryMut<'_, K, V, S, A>
where K: Sync, V: Sync, S: Sync, A: Sync + Allocator,

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impl<K, V, S, A> Sync for OccupiedEntry<'_, K, V, S, A>
where K: Sync, V: Sync, S: Sync, A: Sync + Allocator,

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impl<K, V, S, A> Sync for RawOccupiedEntryMut<'_, K, V, S, A>
where K: Sync, V: Sync, S: Sync, A: Sync + Allocator,

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impl<P, T, const CP: bool> Sync for CopyTaggedPtr<P, T, CP>
where P: Sync + Pointer, T: Sync + Tag,

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impl<R, G> Sync for RawReentrantMutex<R, G>
where R: RawMutex + Sync, G: GetThreadId + Sync,

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impl<R, G, T> Sync for ReentrantMutex<R, G, T>
where R: RawMutex + Sync, G: GetThreadId + Sync, T: Send + ?Sized,

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impl<R, T> Sync for Mutex<R, T>
where R: RawMutex + Sync, T: Send + ?Sized,

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impl<R, T> Sync for RwLock<R, T>
where R: RawRwLock + Sync, T: Send + Sync + ?Sized,

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impl<R, T> Sync for RwLockReadGuard<'_, R, T>
where R: RawRwLock + Sync, T: Sync + ?Sized,

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impl<R, T> Sync for RwLockWriteGuard<'_, R, T>
where R: RawRwLock + Sync, T: Sync + ?Sized,

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impl<T> !Sync for *const T
where T: ?Sized,

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impl<T> !Sync for *mut T
where T: ?Sized,

1.70.0 · source§

impl<T> !Sync for OnceCell<T>

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impl<T> !Sync for Cell<T>
where T: ?Sized,

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impl<T> !Sync for RefCell<T>
where T: ?Sized,

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impl<T> !Sync for UnsafeCell<T>
where T: ?Sized,

1.25.0 · source§

impl<T> !Sync for NonNull<T>
where T: ?Sized,

NonNull pointers are not Sync because the data they reference may be aliased.

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impl<T> !Sync for std::sync::mpsc::Receiver<T>

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impl<T> Sync for ThinBox<T>
where T: Sync + ?Sized,

ThinBox<T> is Sync if T is Sync because the data is owned.

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impl<T> Sync for alloc::collections::linked_list::Iter<'_, T>
where T: Sync,

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impl<T> Sync for alloc::collections::linked_list::IterMut<'_, T>
where T: Sync,

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impl<T> Sync for SyncUnsafeCell<T>
where T: Sync + ?Sized,

1.31.0 · source§

impl<T> Sync for ChunksExactMut<'_, T>
where T: Sync,

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impl<T> Sync for ChunksMut<'_, T>
where T: Sync,

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impl<T> Sync for core::slice::iter::Iter<'_, T>
where T: Sync,

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impl<T> Sync for core::slice::iter::IterMut<'_, T>
where T: Sync,

1.31.0 · source§

impl<T> Sync for RChunksExactMut<'_, T>
where T: Sync,

1.31.0 · source§

impl<T> Sync for RChunksMut<'_, T>
where T: Sync,

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impl<T> Sync for AtomicPtr<T>

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impl<T> Sync for Exclusive<T>
where T: ?Sized,

1.72.0 · source§

impl<T> Sync for std::sync::mpsc::Sender<T>
where T: Send,

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impl<T> Sync for std::sync::mutex::MappedMutexGuard<'_, T>
where T: Sync + ?Sized,

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impl<T> Sync for std::sync::mutex::Mutex<T>
where T: Send + ?Sized,

1.19.0 · source§

impl<T> Sync for std::sync::mutex::MutexGuard<'_, T>
where T: Sync + ?Sized,

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impl<T> Sync for std::sync::rwlock::MappedRwLockReadGuard<'_, T>
where T: Sync + ?Sized,

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impl<T> Sync for std::sync::rwlock::MappedRwLockWriteGuard<'_, T>
where T: Sync + ?Sized,

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impl<T> Sync for std::sync::rwlock::RwLock<T>
where T: Send + Sync + ?Sized,

1.23.0 · source§

impl<T> Sync for std::sync::rwlock::RwLockReadGuard<'_, T>
where T: Sync + ?Sized,

1.23.0 · source§

impl<T> Sync for std::sync::rwlock::RwLockWriteGuard<'_, T>
where T: Sync + ?Sized,

1.29.0 · source§

impl<T> Sync for JoinHandle<T>

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impl<T> Sync for rayon_core::worker_local::WorkerLocal<T>
where T: Send,

We prevent concurrent access to the underlying value in the Deref impl, thus any values safe to send across threads can be used with WorkerLocal.

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impl<T> Sync for ThinVec<T>
where T: Sync,

1.70.0 · source§

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

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impl<T> Sync for Atomic<T>
where T: Pointable + Send + Sync + ?Sized,

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impl<T> Sync for AtomicCell<T>
where T: Send,

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impl<T> Sync for CachePadded<T>
where T: Sync,

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impl<T> Sync for Injector<T>
where T: Send,

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

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impl<T> Sync for Receiver<T>
where T: Send,

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impl<T> Sync for ScopedJoinHandle<'_, T>

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impl<T> Sync for Sender<T>
where T: Send,

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impl<T> Sync for ShardedLock<T>
where T: Send + Sync + ?Sized,

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impl<T> Sync for ShardedLockReadGuard<'_, T>
where T: Sync + ?Sized,

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impl<T> Sync for ShardedLockWriteGuard<'_, T>
where T: Sync + ?Sized,

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impl<T> Sync for Stealer<T>
where T: Send,

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impl<T, A> !Sync for Rc<T, A>
where A: Allocator, T: ?Sized,

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impl<T, A> !Sync for alloc::rc::Weak<T, A>
where A: Allocator, T: ?Sized,

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impl<T, A> Sync for Cursor<'_, T, A>
where T: Sync, A: Allocator + Sync,

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impl<T, A> Sync for CursorMut<'_, T, A>
where T: Sync, A: Allocator + Sync,

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impl<T, A> Sync for LinkedList<T, A>
where T: Sync, A: Allocator + Sync,

1.6.0 · source§

impl<T, A> Sync for alloc::collections::vec_deque::drain::Drain<'_, T, A>
where T: Sync, A: Allocator + Sync,

1.6.0 · source§

impl<T, A> Sync for alloc::vec::drain::Drain<'_, T, A>
where T: Sync, A: Sync + Allocator,

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impl<T, A> Sync for alloc::vec::into_iter::IntoIter<T, A>
where T: Sync, A: Allocator + Sync,

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impl<T, A> Sync for hashbrown::table::OccupiedEntry<'_, T, A>
where T: Sync, A: Sync + Allocator,

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impl<T, A> Sync for Arc<T, A>
where T: Sync + Send + ?Sized, A: Allocator + Sync,

1.4.0 · source§

impl<T, A> Sync for rustc_data_structures::sync::Weak<T, A>
where T: Sync + Send + ?Sized, A: Allocator + Sync,

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impl<T, A> Sync for Box<T, A>
where A: Allocator + Sync, T: Sync + ?Sized,

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impl<T, A> Sync for Drain<'_, T, A>
where T: Sync, A: Sync + Allocator,

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impl<T, A> Sync for IntoIter<T, A>
where T: Sync, A: Allocator + Sync,

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impl<T, A> Sync for OccupiedEntry<'_, T, A>
where T: Sync, A: Sync + Allocator,

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impl<T, A> Sync for RawDrain<'_, T, A>
where A: Allocator + Sync, T: Sync,

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impl<T, A> Sync for RawIntoIter<T, A>
where A: Allocator + Sync, T: Sync,

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impl<T, A> Sync for RawTable<T, A>
where A: Allocator + Sync, T: Sync,

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impl<T, F> Sync for LazyLock<T, F>
where T: Sync + Send, F: Send,

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impl<T, F> Sync for Lazy<T, F>
where F: Send, OnceCell<T>: Sync,

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impl<T, F, S> Sync for ScopeGuard<T, F, S>
where T: Sync, F: FnOnce(T), S: Strategy,

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impl<T: DynSync> Sync for FromDyn<T>

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impl<T: Send> Sync for rustc_data_structures::sync::worker_local::WorkerLocal<T>

Auto implementors§

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impl !Sync for RegistryId

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impl !Sync for ThreadData

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impl !Sync for ModeUnion

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impl Sync for NodeStatus

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impl Sync for rustc_data_structures::obligation_forest::NodeState

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impl Sync for TimePassesFormat

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impl Sync for Mode

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impl Sync for Fingerprint

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impl Sync for PackedFingerprint

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impl Sync for rustc_data_structures::flock::linux::Lock

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impl Sync for FxHasher

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impl Sync for PreorderIndex

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impl Sync for Time

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impl Sync for Direction

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impl Sync for EdgeIndex

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impl Sync for NodeIndex

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impl Sync for CycleDetector

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impl Sync for PrivateZst

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impl Sync for Client

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impl Sync for Mmap

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impl Sync for MmapMut

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impl Sync for ObligationTreeId

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impl Sync for Pu128

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impl Sync for EventFilter

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impl Sync for EventId

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impl Sync for QueryInvocationId

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impl Sync for SelfProfiler

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impl Sync for SelfProfilerRef

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impl Sync for VerboseInfo

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impl Sync for Sip13Rounds

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impl Sync for SipHasher128

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impl Sync for State

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impl Sync for SmallCStr

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impl Sync for Hash64

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impl Sync for Hash128

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impl Sync for HashingControls

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impl Sync for StableHasher

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impl Sync for FatalErrorMarker

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impl Sync for Svh

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impl Sync for MaybeTempDir

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impl Sync for rustc_data_structures::transitive_relation::Edge

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impl Sync for Index

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impl Sync for NoUndo

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impl Sync for rustc_data_structures::undo_log::Snapshot

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impl Sync for Unhasher

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impl Sync for NoError

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impl Sync for ParallelGuard

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impl Sync for Registry

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impl Sync for RegistryData

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impl<'a> Sync for JsonTimePassesEntry<'a>

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impl<'a> Sync for TimingGuard<'a>

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impl<'a> Sync for VerboseTimingGuard<'a>

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impl<'a, K, V> Sync for Entry<'a, K, V>
where K: Sync, V: Sync,

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impl<'a, T> !Sync for FreezeReadGuard<'a, T>

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impl<'a, T> !Sync for FreezeWriteGuard<'a, T>

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impl<'a, T> !Sync for LockGuard<'a, T>

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impl<'a, T> Sync for Interned<'a, T>
where T: Sync,

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impl<'b, T> !Sync for RefMut<'b, T>

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impl<'c, G, S> Sync for SccsConstruction<'c, G, S>
where G: Sync, S: Sync, <G as DirectedGraph>::Node: Sync,

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impl<'g, N, E> Sync for AdjacentEdges<'g, N, E>
where E: Sync, N: Sync,

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impl<'g, N, E> Sync for DepthFirstTraversal<'g, N, E>
where E: Sync, N: Sync,

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impl<'graph, G: ?Sized> Sync for DepthFirstSearch<'graph, G>
where G: Sync, <G as DirectedGraph>::Node: Sync,

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impl<'graph, G: ?Sized> Sync for TriColorDepthFirstSearch<'graph, G>
where G: Sync, <G as DirectedGraph>::Node: Sync,

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impl<'p> Sync for EventArgRecorder<'p>

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impl<D> Sync for rustc_data_structures::snapshot_vec::UndoLog<D>

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impl<D, V, L> Sync for SnapshotVec<D, V, L>
where D: Sync, L: Sync, V: Sync,

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impl<E> Sync for rustc_data_structures::graph::implementation::Edge<E>
where E: Sync,

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impl<F> Sync for OnDrop<F>
where F: Sync,

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impl<I, K, V> Sync for SortedIndexMultiMap<I, K, V>
where I: Sync, K: Sync, V: Sync,

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impl<I, T> Sync for AppendOnlyIndexVec<I, T>

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impl<Iter> Sync for PreOrderFrame<Iter>
where Iter: Sync,

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impl<K> Sync for VarValue<K>
where K: Sync, <K as UnifyKey>::Value: Sync,

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impl<K, V> Sync for rustc_data_structures::snapshot_map::UndoLog<K, V>
where K: Sync, V: Sync,

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impl<K, V> Sync for SsoHashMap<K, V>
where K: Sync, V: Sync,

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impl<K, V> Sync for SortedMap<K, V>
where K: Sync, V: Sync,

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impl<K, V> Sync for UnordMap<K, V>
where K: Sync, V: Sync,

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impl<K, V, L> Sync for InPlace<K, V, L>
where K: Sync, L: Sync, V: Sync,

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impl<K, V, M, L> Sync for SnapshotMap<K, V, M, L>
where K: Sync, L: Sync, M: Sync, V: Sync,

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impl<Ls> Sync for VecLinkedListIterator<Ls>
where Ls: Sync, <Ls as Links>::LinkIndex: Sync,

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impl<N> Sync for Inner<N>
where N: Sync,

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impl<N> Sync for rustc_data_structures::graph::implementation::Node<N>
where N: Sync,

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impl<N> Sync for Event<N>
where N: Sync,

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impl<N> Sync for VecGraph<N>
where N: Sync,

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impl<N, E> Sync for Graph<N, E>
where E: Sync, N: Sync,

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impl<N, S> Sync for rustc_data_structures::graph::scc::NodeState<N, S>
where N: Sync, S: Sync,

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impl<N, S> Sync for Sccs<N, S>
where S: Sync,

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impl<Node> Sync for Kind<Node>
where Node: Sync,

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impl<Node> Sync for Dominators<Node>
where Node: Sync,

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impl<O> !Sync for rustc_data_structures::obligation_forest::Node<O>

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impl<O> !Sync for ObligationForest<O>

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impl<O, E> Sync for ProcessResult<O, E>
where E: Sync, O: Sync,

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impl<O, E> Sync for Error<O, E>
where E: Sync, O: Sync,

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impl<O, E> Sync for Outcome<O, E>
where E: Sync, O: Sync,

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impl<P, T, const COMPARE_PACKED: bool> Sync for TaggedPtr<P, T, COMPARE_PACKED>
where P: Sync, T: Sync,

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impl<S> Sync for WalkReturn<S>
where S: Sync,

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impl<S> Sync for SccData<S>
where S: Sync,

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impl<S> Sync for rustc_data_structures::snapshot_vec::Snapshot<S>
where S: Sync,

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impl<S> Sync for rustc_data_structures::unify::Snapshot<S>
where S: Sync, <S as UnificationStore>::Snapshot: Sync,

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impl<S> Sync for UnificationTable<S>
where S: Sync,

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impl<T> !Sync for Sharded<T>

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impl<T> !Sync for FreezeLock<T>

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impl<T> !Sync for rustc_data_structures::sync::lock::maybe_sync::Lock<T>

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impl<T> !Sync for rustc_data_structures::sync::lock::no_sync::Lock<T>

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impl<T> !Sync for MTLock<T>

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impl<T> Sync for AtomicRef<T>
where T: Sync,

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impl<T> Sync for Frozen<T>
where T: Sync,

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impl<T> Sync for SsoHashSet<T>
where T: Sync,

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

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impl<T> Sync for Element<T>
where T: Sync,

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impl<T> Sync for TinyList<T>
where T: Sync,

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impl<T> Sync for TransitiveRelation<T>
where T: Sync,

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impl<T> Sync for TransitiveRelationBuilder<T>
where T: Sync,

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impl<T> Sync for VecLog<T>
where T: Sync,

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impl<T> Sync for WorkQueue<T>
where T: Sync,

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impl<T> Sync for CacheAligned<T>
where T: Sync,

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impl<T> Sync for rustc_data_structures::sync::RwLock<T>
where T: Sync + Send,

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

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impl<T, I> Sync for UnordItems<T, I>
where I: Sync,

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impl<T: ?Sized> Sync for IntoDynSyncSend<T>
where T: Sync,

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impl<V> Sync for UnordBag<V>
where V: Sync,

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impl<V> Sync for UnordSet<V>
where V: Sync,