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/*!
Zero-sized types .
*/

use std::{marker::PhantomData, rc::Rc};

use crate::{derive_macro_reexports::*, std_types::RNone};



/// Marker type used to mark a type as being Send+Sync.
pub struct SyncSend;

/// Marker type used to mark a type as being !Send+!Sync.
pub struct UnsyncUnsend {
    _marker: PhantomData<Rc<()>>,
}



#[repr(C)]
/// A Zero-sized type used by `VirtualWrapper<Pointer<OpaqueType<T>>>`.
///
/// If this did not wrap `T`,
/// we could pretend to have a `T` even though we don't.
///
/// Casting the pointer type to point to this type is safe,
/// because the pointer is required to be castable to point to different types,
/// so long as a reference to one is valid for the other.
///
/// This type intentionally does not implement any traits.
pub struct OpaqueType<T> {
    _priv: [u8; 0],
    _inner: PhantomData<T>,
}

/// Used by vtables/pointers to signal that the type has been erased.
///
/// Also,because `()` implements InterfaceType,
/// `VirtualWrapper<Pointer<ErasedObject>>`
/// can be created by calling `VirtualWrapper::from_any_ptr(ptr,())`;
///
pub type ErasedObject = OpaqueType<()>;

unsafe impl<T> StableAbi for OpaqueType<T> {
    type IsNonZeroType = False;
    const LAYOUT: &'static TypeLayout = &TypeLayout::from_std_lib_primitive::<Self>(
        "OpaqueType",
        RNone,
        TLData::Primitive,
        tl_genparams!(;;),
    );
}