diff options
| -rw-r--r-- | rust/pin-init/src/lib.rs | 32 |
1 files changed, 32 insertions, 0 deletions
diff --git a/rust/pin-init/src/lib.rs b/rust/pin-init/src/lib.rs index 0806c689f693..a880c21d3f09 100644 --- a/rust/pin-init/src/lib.rs +++ b/rust/pin-init/src/lib.rs @@ -1216,6 +1216,38 @@ pub const unsafe fn init_from_closure<T: ?Sized, E>( __internal::InitClosure(f, PhantomData) } +/// Changes the to be initialized type. +/// +/// # Safety +/// +/// - `*mut U` must be castable to `*mut T` and any value of type `T` written through such a +/// pointer must result in a valid `U`. +#[expect(clippy::let_and_return)] +pub const unsafe fn cast_pin_init<T, U, E>(init: impl PinInit<T, E>) -> impl PinInit<U, E> { + // SAFETY: initialization delegated to a valid initializer. Cast is valid by function safety + // requirements. + let res = unsafe { pin_init_from_closure(|ptr: *mut U| init.__pinned_init(ptr.cast::<T>())) }; + // FIXME: remove the let statement once the nightly-MSRV allows it (1.78 otherwise encounters a + // cycle when computing the type returned by this function) + res +} + +/// Changes the to be initialized type. +/// +/// # Safety +/// +/// - `*mut U` must be castable to `*mut T` and any value of type `T` written through such a +/// pointer must result in a valid `U`. +#[expect(clippy::let_and_return)] +pub const unsafe fn cast_init<T, U, E>(init: impl Init<T, E>) -> impl Init<U, E> { + // SAFETY: initialization delegated to a valid initializer. Cast is valid by function safety + // requirements. + let res = unsafe { init_from_closure(|ptr: *mut U| init.__init(ptr.cast::<T>())) }; + // FIXME: remove the let statement once the nightly-MSRV allows it (1.78 otherwise encounters a + // cycle when computing the type returned by this function) + res +} + /// An initializer that leaves the memory uninitialized. /// /// The initializer is a no-op. The `slot` memory is not changed. |