Trait swc_common::sync::Sync

#[lang = "sync"]
pub unsafe auto trait Sync { }

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.

Types that are not Sync are those that have "interior mutability" in a non-thread-safe form, such as cell::Cell and cell::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::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.

Implementations on Foreign Types

impl<T> Sync for Key<T>

impl<T> Sync for JoinHandle<T>

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

impl<T> !Sync for Sender<T>

impl<'a, T> Sync for RwLockReadGuard<'a, T> where     T: Sync + ?Sized,

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

impl<'a, T> Sync for RwLockWriteGuard<'a, T> where     T: Sync + ?Sized,

impl !Sync for ArgsOs

impl<T> !Sync for Receiver<T>

impl Sync for Once

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

impl !Sync for Args

impl Sync for AtomicU8

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

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

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

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

impl Sync for AtomicU16

impl Sync for AtomicI32

impl<T> Sync for AtomicPtr<T>

impl !Sync for LocalWaker

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

impl Sync for AtomicU32

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

impl Sync for AtomicI8

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

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

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

impl Sync for AtomicI16

impl Sync for AtomicU64

impl Sync for AtomicIsize

impl Sync for Waker

impl Sync for AtomicI64

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

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

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

impl<'a> Sync for Drain<'a>

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

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

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

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

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

impl<O, T> Sync for OwningRefMut<O, T> where     O: Sync,     T: ?Sized,     &'a mut T: Sync,

impl<O, T> Sync for OwningRef<O, T> where     O: Sync,     T: ?Sized,     &'a T: Sync,

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

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

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

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

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

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

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

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

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

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

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

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

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

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

impl Sync for Collector

impl<'a, A> Sync for Drain<'a, A> where     A: Array + Sync,

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

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

impl<T> Sync for ScopedKey<T>

impl Sync for isize

impl Sync for i8

impl Sync for i16

impl Sync for i32

impl Sync for i64

impl Sync for i128

impl Sync for usize

impl Sync for u8

impl Sync for u16

impl Sync for u32

impl Sync for u64

impl Sync for u128

impl Sync for f32

impl Sync for f64

impl Sync for f32

impl Sync for f64

impl Sync for char

impl Sync for str

impl Sync for str

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Implementors

impl Sync for AtomicBool

impl Sync for AtomicUsize

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

impl<T> Sync for OneThread<T>

impl<T> Sync for swc_common::sync::Weak<T> where     T: Send + Sync + ?Sized,

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Auto implementors

impl !Sync for Destination

impl !Sync for EmitterWriter

impl Sync for FileName

impl Sync for SpanSnippetError

impl Sync for ColorConfig

impl Sync for Applicability

impl Sync for DiagnosticId

impl Sync for Level

impl Sync for Transparency

impl Sync for Ordering

impl Sync for Registry

impl Sync for CodeSuggestion

impl Sync for Diagnostic

impl Sync for DiagnosticStyledString

impl Sync for ExplicitBug

impl Sync for FatalError

impl Sync for FatalErrorMarker

impl Sync for Handler

impl Sync for HandlerFlags

impl Sync for SubDiagnostic

impl Sync for Substitution

impl Sync for SubstitutionPart

impl Sync for BytePos

impl Sync for ExpnInfo

impl Sync for FileLines

impl Sync for FilePathMapping

impl Sync for Globals

impl Sync for Mark

impl Sync for MultiSpan

impl Sync for SourceFile

impl Sync for SourceMap

impl Sync for Span

impl Sync for SpanData

impl Sync for SyntaxContext

impl Sync for SerialScope

impl<'a> !Sync for WritableDst<'a>

impl<'a> Sync for DiagnosticBuilder<'a>

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

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

impl<T> Sync for swc_common::sync::Once<T> where     T: Send + Sync,

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

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