Struct abi_stable::type_level::downcasting::TD_Opaque

pub struct TD_Opaque;

Passed to trait object constructors to make it impossible to downcast the trait object, as opposed to TD_CanDowncast.

The from_value/from_ptr/from_const methods here take this type.

Example

use abi_stable::{
    sabi_trait::doc_examples::Action_TO,
    std_types::RBox,
    type_level::downcasting::TD_Opaque,
};

// The type annotation is purely for the reader.
let mut object: Action_TO<'static, RBox<()>> =
    Action_TO::from_value(100_usize, TD_Opaque);

assert_eq!(object.obj.downcast_as::<u8>().ok(), None);

assert_eq!(object.obj.downcast_as::<char>().ok(), None);

// Because `Action_TO::from-value` was passed `TD_Opaque`,
// the trait object can't be downcasted
assert_eq!(object.obj.downcast_as::<usize>().ok(), None);

Trait Implementations

impl Clone for TD_Opaque

fn clone(&self) -> TD_Opaque

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T> GetUTID<T> for TD_Opaque

const UID: extern "C" fn() -> MaybeCmp<UTypeId> = {std_types::utypeid::no_utypeid as extern "C" fn() -> sabi_types::maybe_cmp::MaybeCmp<std_types::utypeid::UTypeId>}

the function.

impl Copy for TD_Opaque