Trait core::marker::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.

Implementors§

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impl !Sync for LocalWaker

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impl Sync for AtomicBool

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

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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 Waker

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

1.70.0 · source§

impl<T> !Sync for OnceCell<T>

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

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

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

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

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

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

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

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

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

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

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

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

Auto implementors§

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impl !Sync for RawWaker

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impl Sync for AsciiChar

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impl Sync for core::cmp::Ordering

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impl Sync for Infallible

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impl Sync for c_void

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impl Sync for core::fmt::Alignment

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impl Sync for BasicBlock

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impl Sync for UnwindTerminateReason

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impl Sync for IpAddr

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impl Sync for Ipv6MulticastScope

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impl Sync for SocketAddr

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impl Sync for FpCategory

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impl Sync for IntErrorKind

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impl Sync for SearchStep

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impl Sync for core::sync::atomic::Ordering

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impl Sync for bool

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impl Sync for char

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impl Sync for f32

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impl Sync for f64

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impl Sync for i8

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impl Sync for i16

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impl Sync for i32

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impl Sync for i64

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impl Sync for i128

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impl Sync for isize

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impl Sync for str

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impl Sync for u8

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impl Sync for u16

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impl Sync for u32

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impl Sync for u64

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impl Sync for u128

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impl Sync for ()

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impl Sync for usize

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impl Sync for AllocError

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impl Sync for Layout

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impl Sync for LayoutError

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impl Sync for TypeId

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impl Sync for float64x1_t

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impl Sync for float64x1x2_t

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impl Sync for float64x1x3_t

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impl Sync for float64x1x4_t

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impl Sync for float64x2_t

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impl Sync for float64x2x2_t

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impl Sync for float64x2x3_t

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impl Sync for float64x2x4_t

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impl Sync for SY

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impl Sync for float32x2_t

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impl Sync for float32x2x2_t

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impl Sync for float32x2x3_t

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impl Sync for float32x2x4_t

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impl Sync for float32x4_t

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impl Sync for float32x4x2_t

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impl Sync for float32x4x3_t

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impl Sync for float32x4x4_t

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impl Sync for int8x4_t

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impl Sync for int8x8_t

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impl Sync for int8x8x2_t

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impl Sync for int8x8x3_t

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impl Sync for int8x8x4_t

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impl Sync for int8x16_t

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impl Sync for int8x16x2_t

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impl Sync for int8x16x3_t

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impl Sync for int8x16x4_t

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impl Sync for int16x2_t

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impl Sync for int16x4_t

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impl Sync for int16x4x2_t

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impl Sync for int16x4x3_t

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impl Sync for int16x4x4_t

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impl Sync for int16x8_t

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impl Sync for int16x8x2_t

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impl Sync for int16x8x3_t

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impl Sync for int16x8x4_t

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impl Sync for int32x2_t

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impl Sync for int32x2x2_t

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impl Sync for int32x2x3_t

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impl Sync for int32x2x4_t

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impl Sync for int32x4_t

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impl Sync for int32x4x2_t

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impl Sync for int32x4x3_t

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impl Sync for int32x4x4_t

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impl Sync for int64x1_t

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impl Sync for int64x1x2_t

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impl Sync for int64x1x3_t

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impl Sync for int64x1x4_t

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impl Sync for int64x2_t

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impl Sync for int64x2x2_t

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impl Sync for int64x2x3_t

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impl Sync for int64x2x4_t

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impl Sync for poly8x8_t

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impl Sync for poly8x8x2_t

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impl Sync for poly8x8x3_t

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impl Sync for poly8x8x4_t

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impl Sync for poly8x16_t

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impl Sync for poly8x16x2_t

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impl Sync for poly8x16x3_t

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impl Sync for poly8x16x4_t

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impl Sync for poly16x4_t

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impl Sync for poly16x4x2_t

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impl Sync for poly16x4x3_t

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impl Sync for poly16x4x4_t

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impl Sync for poly16x8_t

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impl Sync for poly16x8x2_t

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impl Sync for poly16x8x3_t

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impl Sync for poly16x8x4_t

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impl Sync for poly64x1_t

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impl Sync for poly64x1x2_t

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impl Sync for poly64x1x3_t

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impl Sync for poly64x1x4_t

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impl Sync for poly64x2_t

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impl Sync for poly64x2x2_t

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impl Sync for poly64x2x3_t

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impl Sync for poly64x2x4_t

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impl Sync for uint8x4_t

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impl Sync for uint8x8_t

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impl Sync for uint8x8x2_t

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impl Sync for uint8x8x3_t

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impl Sync for uint8x8x4_t

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impl Sync for uint8x16_t

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impl Sync for uint8x16x2_t

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impl Sync for uint8x16x3_t

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impl Sync for uint8x16x4_t

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impl Sync for uint16x2_t

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impl Sync for uint16x4_t

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impl Sync for uint16x4x2_t

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impl Sync for uint16x4x3_t

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impl Sync for uint16x4x4_t

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impl Sync for uint16x8_t

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impl Sync for uint16x8x2_t

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impl Sync for uint16x8x3_t

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impl Sync for uint16x8x4_t

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impl Sync for uint32x2_t

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impl Sync for uint32x2x2_t

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impl Sync for uint32x2x3_t

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impl Sync for uint32x2x4_t

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impl Sync for uint32x4_t

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impl Sync for uint32x4x2_t

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impl Sync for uint32x4x3_t

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impl Sync for uint32x4x4_t

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impl Sync for uint64x1_t

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impl Sync for uint64x1x2_t

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impl Sync for uint64x1x3_t

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impl Sync for uint64x1x4_t

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impl Sync for uint64x2_t

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impl Sync for uint64x2x2_t

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impl Sync for uint64x2x3_t

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impl Sync for uint64x2x4_t

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impl Sync for vector_bool_char

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impl Sync for vector_bool_int

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impl Sync for vector_bool_long

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impl Sync for vector_bool_short

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impl Sync for vector_double

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impl Sync for vector_float

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impl Sync for vector_signed_char

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impl Sync for vector_signed_int

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impl Sync for vector_signed_long

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impl Sync for vector_signed_short

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impl Sync for vector_unsigned_char

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impl Sync for vector_unsigned_int

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impl Sync for vector_unsigned_long

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impl Sync for vector_unsigned_short

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impl Sync for v128

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impl Sync for CpuidResult

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impl Sync for __m128

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impl Sync for __m128bh

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impl Sync for __m128d

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impl Sync for __m128i

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impl Sync for __m256

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impl Sync for __m256bh

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impl Sync for __m256d

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impl Sync for __m256i

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impl Sync for __m512

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impl Sync for __m512bh

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impl Sync for __m512d

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impl Sync for __m512i

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impl Sync for TryFromSliceError

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impl Sync for core::ascii::EscapeDefault

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impl Sync for BorrowError

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impl Sync for BorrowMutError

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impl Sync for CharTryFromError

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impl Sync for DecodeUtf16Error

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impl Sync for core::char::EscapeDebug

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impl Sync for core::char::EscapeDefault

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impl Sync for core::char::EscapeUnicode

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impl Sync for ParseCharError

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impl Sync for ToLowercase

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impl Sync for ToUppercase

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impl Sync for TryFromCharError

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impl Sync for CStr

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impl Sync for FromBytesUntilNulError

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impl Sync for FromBytesWithNulError

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impl Sync for Error

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impl Sync for SipHasher

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impl Sync for ReturnToArg

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impl Sync for UnwindActionArg

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impl Sync for Assume

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impl Sync for AddrParseError

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impl Sync for Ipv4Addr

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impl Sync for Ipv6Addr

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impl Sync for SocketAddrV4

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impl Sync for SocketAddrV6

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impl Sync for ParseFloatError

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impl Sync for ParseIntError

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impl Sync for TryFromIntError

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impl Sync for RangeFull

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impl Sync for core::ptr::Alignment

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impl Sync for TimSortRun

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impl Sync for ParseBoolError

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impl Sync for Utf8Error

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impl Sync for RawWakerVTable

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impl Sync for Duration

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impl Sync for TryFromFloatSecsError

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impl Sync for PhantomPinned

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

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

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

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

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

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

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

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impl<'a> Sync for BorrowedCursor<'a>

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impl<'a> Sync for Location<'a>

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impl<'a> Sync for EscapeAscii<'a>

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impl<'a> Sync for CharSearcher<'a>

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impl<'a> Sync for Bytes<'a>

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impl<'a> Sync for CharIndices<'a>

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impl<'a> Sync for Chars<'a>

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impl<'a> Sync for EncodeUtf16<'a>

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impl<'a> Sync for core::str::EscapeDebug<'a>

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impl<'a> Sync for core::str::EscapeDefault<'a>

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impl<'a> Sync for core::str::EscapeUnicode<'a>

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impl<'a> Sync for Lines<'a>

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impl<'a> Sync for LinesAny<'a>

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impl<'a> Sync for SplitAsciiWhitespace<'a>

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impl<'a> Sync for SplitWhitespace<'a>

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impl<'a> Sync for Utf8Chunk<'a>

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impl<'a> Sync for Utf8Chunks<'a>

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impl<'a, 'b> !Sync for DebugList<'a, 'b>

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impl<'a, 'b> !Sync for DebugMap<'a, 'b>

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impl<'a, 'b> !Sync for DebugSet<'a, 'b>

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impl<'a, 'b> !Sync for DebugStruct<'a, 'b>

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impl<'a, 'b> !Sync for DebugTuple<'a, 'b>

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impl<'a, 'b> Sync for CharSliceSearcher<'a, 'b>

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impl<'a, 'b> Sync for StrSearcher<'a, 'b>

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impl<'a, 'b, const N: usize> Sync for CharArrayRefSearcher<'a, 'b, N>

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impl<'a, 'f> !Sync for VaList<'a, 'f>

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impl<'a, A> Sync for core::option::Iter<'a, A>
where A: Sync,

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impl<'a, A> Sync for core::option::IterMut<'a, A>
where A: Sync,

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impl<'a, F> Sync for CharPredicateSearcher<'a, F>
where F: Sync,

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impl<'a, I> Sync for ByRefSized<'a, I>
where I: Sync,

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impl<'a, P> Sync for MatchIndices<'a, P>
where <P as Pattern<'a>>::Searcher: Sync,

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impl<'a, P> Sync for Matches<'a, P>
where <P as Pattern<'a>>::Searcher: Sync,

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impl<'a, P> Sync for RMatchIndices<'a, P>
where <P as Pattern<'a>>::Searcher: Sync,

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impl<'a, P> Sync for RMatches<'a, P>
where <P as Pattern<'a>>::Searcher: Sync,

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impl<'a, P> Sync for core::str::RSplit<'a, P>
where <P as Pattern<'a>>::Searcher: Sync,

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impl<'a, P> Sync for core::str::RSplitN<'a, P>
where <P as Pattern<'a>>::Searcher: Sync,

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impl<'a, P> Sync for RSplitTerminator<'a, P>
where <P as Pattern<'a>>::Searcher: Sync,

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impl<'a, P> Sync for core::str::Split<'a, P>
where <P as Pattern<'a>>::Searcher: Sync,

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impl<'a, P> Sync for core::str::SplitInclusive<'a, P>
where <P as Pattern<'a>>::Searcher: Sync,

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impl<'a, P> Sync for core::str::SplitN<'a, P>
where <P as Pattern<'a>>::Searcher: Sync,

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impl<'a, P> Sync for SplitTerminator<'a, P>
where <P as Pattern<'a>>::Searcher: Sync,

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

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

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

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

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

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

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

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impl<'a, T, P> Sync for ChunkBy<'a, T, P>
where P: Sync, T: Sync,

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impl<'a, T, P> Sync for ChunkByMut<'a, T, P>
where P: Sync, T: Sync,

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impl<'a, T, P> Sync for core::slice::RSplit<'a, T, P>
where P: Sync, T: Sync,

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impl<'a, T, P> Sync for RSplitMut<'a, T, P>
where P: Sync, T: Sync,

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impl<'a, T, P> Sync for core::slice::RSplitN<'a, T, P>
where P: Sync, T: Sync,

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impl<'a, T, P> Sync for RSplitNMut<'a, T, P>
where P: Sync, T: Sync,

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impl<'a, T, P> Sync for core::slice::Split<'a, T, P>
where P: Sync, T: Sync,

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impl<'a, T, P> Sync for core::slice::SplitInclusive<'a, T, P>
where P: Sync, T: Sync,

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impl<'a, T, P> Sync for SplitInclusiveMut<'a, T, P>
where P: Sync, T: Sync,

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impl<'a, T, P> Sync for SplitMut<'a, T, P>
where P: Sync, T: Sync,

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impl<'a, T, P> Sync for core::slice::SplitN<'a, T, P>
where P: Sync, T: Sync,

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impl<'a, T, P> Sync for SplitNMut<'a, T, P>
where P: Sync, T: Sync,

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impl<'a, T, const N: usize> !Sync for ArrayWindows<'a, T, N>

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impl<'a, T, const N: usize> Sync for core::slice::ArrayChunks<'a, T, N>
where T: Sync,

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impl<'a, T, const N: usize> Sync for ArrayChunksMut<'a, T, N>
where T: Sync,

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impl<'a, const N: usize> Sync for CharArraySearcher<'a, N>

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

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

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impl<'data> Sync for BorrowedBuf<'data>

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impl<'f> !Sync for VaListImpl<'f>

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impl<A> Sync for Repeat<A>
where A: Sync,

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impl<A> Sync for RepeatN<A>
where A: Sync,

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impl<A> Sync for core::option::IntoIter<A>
where A: Sync,

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impl<A, B> Sync for Chain<A, B>
where A: Sync, B: Sync,

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impl<A, B> Sync for Zip<A, B>
where A: Sync, B: Sync,

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impl<B, C> Sync for ControlFlow<B, C>
where B: Sync, C: Sync,

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

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

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

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

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

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impl<H> Sync for BuildHasherDefault<H>

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impl<I> Sync for FromIter<I>
where I: Sync,

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impl<I> Sync for DecodeUtf16<I>
where I: Sync,

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impl<I> Sync for Cloned<I>
where I: Sync,

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impl<I> Sync for Copied<I>
where I: Sync,

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impl<I> Sync for Cycle<I>
where I: Sync,

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impl<I> Sync for Enumerate<I>
where I: Sync,

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impl<I> Sync for Flatten<I>
where I: Sync, <<I as Iterator>::Item as IntoIterator>::IntoIter: Sync,

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impl<I> Sync for Fuse<I>
where I: Sync,

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impl<I> Sync for Intersperse<I>
where I: Sync, <I as Iterator>::Item: Sync,

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impl<I> Sync for Peekable<I>
where I: Sync, <I as Iterator>::Item: Sync,

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impl<I> Sync for Skip<I>
where I: Sync,

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impl<I> Sync for StepBy<I>
where I: Sync,

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impl<I> Sync for Take<I>
where I: Sync,

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impl<I, F> Sync for FilterMap<I, F>
where F: Sync, I: Sync,

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impl<I, F> Sync for Inspect<I, F>
where F: Sync, I: Sync,

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impl<I, F> Sync for Map<I, F>
where F: Sync, I: Sync,

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impl<I, F, const N: usize> Sync for MapWindows<I, F, N>
where F: Sync, I: Sync, <I as Iterator>::Item: Sync,

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impl<I, G> Sync for IntersperseWith<I, G>
where G: Sync, I: Sync, <I as Iterator>::Item: Sync,

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impl<I, P> Sync for Filter<I, P>
where I: Sync, P: Sync,

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impl<I, P> Sync for MapWhile<I, P>
where I: Sync, P: Sync,

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impl<I, P> Sync for SkipWhile<I, P>
where I: Sync, P: Sync,

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impl<I, P> Sync for TakeWhile<I, P>
where I: Sync, P: Sync,

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impl<I, St, F> Sync for Scan<I, St, F>
where F: Sync, I: Sync, St: Sync,

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impl<I, U, F> Sync for FlatMap<I, U, F>
where F: Sync, I: Sync, <U as IntoIterator>::IntoIter: Sync,

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impl<I, const N: usize> Sync for core::iter::ArrayChunks<I, N>
where I: Sync, <I as Iterator>::Item: Sync,

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impl<Idx> Sync for Range<Idx>
where Idx: Sync,

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impl<Idx> Sync for RangeFrom<Idx>
where Idx: Sync,

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impl<Idx> Sync for RangeInclusive<Idx>
where Idx: Sync,

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impl<Idx> Sync for RangeTo<Idx>
where Idx: Sync,

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impl<Idx> Sync for RangeToInclusive<Idx>
where Idx: Sync,

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impl<Ptr> Sync for Pin<Ptr>
where Ptr: Sync,

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impl<Ret, T> Sync for fn(T₁, T₂, …, Tₙ) -> Ret

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

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

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

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impl<T> Sync for [T]
where T: Sync,

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impl<T> Sync for (T₁, T₂, …, Tₙ)
where T: Sync,

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

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impl<T> Sync for Pending<T>

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

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impl<T> Sync for Empty<T>

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

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

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impl<T> Sync for Discriminant<T>

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

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

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

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

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

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

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

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impl<T, E> Sync for Result<T, E>
where E: Sync, T: Sync,

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impl<T, F = fn() -> T> !Sync for LazyCell<T, F>

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impl<T, F> Sync for Successors<T, F>
where F: Sync, T: Sync,

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impl<T, const N: usize> Sync for [T; N]
where T: Sync,

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impl<T, const N: usize> Sync for core::array::IntoIter<T, N>
where T: Sync,

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impl<T, const N: usize> Sync for Mask<T, N>
where T: Sync,

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impl<T, const N: usize> Sync for Simd<T, N>
where T: Sync,

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impl<T, const N: usize> Sync for [MaybeUninit<T>; N]
where T: Sync,

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

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

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impl<Y, R> Sync for CoroutineState<Y, R>
where R: Sync, Y: Sync,

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impl<const N: usize> Sync for LaneCount<N>

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impl<const N: usize> Sync for GetManyMutError<N>

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impl<const N: usize> Sync for [u8; N]