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|
// Original code (./pinned_drop.rs):
//
// ```rust
// #![allow(dead_code)]
//
// use std::pin::Pin;
//
// use pin_project::{pin_project, pinned_drop};
//
// #[pin_project(PinnedDrop)]
// pub struct Struct<'a, T> {
// was_dropped: &'a mut bool,
// #[pin]
// field: T,
// }
//
// #[pinned_drop]
// fn drop_Struct<T>(mut this: Pin<&mut Struct<'_, T>>) {
// **this.project().was_dropped = true;
// }
//
// fn main() {}
// ```
#![allow(dead_code, unused_imports, unused_parens, unknown_lints, renamed_and_removed_lints)]
#![allow(clippy::needless_lifetimes, clippy::mut_mut)]
use std::pin::Pin;
use pin_project::{pin_project, pinned_drop};
// #[pin_project(PinnedDrop)]
pub struct Struct<'a, T> {
was_dropped: &'a mut bool,
// #[pin]
field: T,
}
const _: () = {
pub(crate) struct __StructProjection<'pin, 'a, T>
where
Struct<'a, T>: 'pin,
{
was_dropped: &'pin mut (&'a mut bool),
field: ::pin_project::__private::Pin<&'pin mut (T)>,
}
pub(crate) struct __StructProjectionRef<'pin, 'a, T>
where
Struct<'a, T>: 'pin,
{
was_dropped: &'pin (&'a mut bool),
field: ::pin_project::__private::Pin<&'pin (T)>,
}
impl<'a, T> Struct<'a, T> {
pub(crate) fn project<'pin>(
self: ::pin_project::__private::Pin<&'pin mut Self>,
) -> __StructProjection<'pin, 'a, T> {
unsafe {
let Self { was_dropped, field } = self.get_unchecked_mut();
__StructProjection {
was_dropped,
field: ::pin_project::__private::Pin::new_unchecked(field),
}
}
}
pub(crate) fn project_ref<'pin>(
self: ::pin_project::__private::Pin<&'pin Self>,
) -> __StructProjectionRef<'pin, 'a, T> {
unsafe {
let Self { was_dropped, field } = self.get_ref();
__StructProjectionRef {
was_dropped,
field: ::pin_project::__private::Pin::new_unchecked(field),
}
}
}
}
// Ensure that it's impossible to use pin projections on a #[repr(packed)]
// struct.
//
// See ./struct-default-expanded.rs and https://github.com/taiki-e/pin-project/pull/34
// for details.
#[forbid(unaligned_references, safe_packed_borrows)]
fn __assert_not_repr_packed<'a, T>(this: &Struct<'a, T>) {
let _ = &this.was_dropped;
let _ = &this.field;
}
impl<'a, T> ::pin_project::__private::Drop for Struct<'a, T> {
fn drop(&mut self) {
// Safety - we're in 'drop', so we know that 'self' will
// never move again.
let pinned_self = unsafe { ::pin_project::__private::Pin::new_unchecked(self) };
// We call `pinned_drop` only once. Since `PinnedDrop::drop`
// is an unsafe method and a private API, it is never called again in safe
// code *unless the user uses a maliciously crafted macro*.
unsafe {
::pin_project::__private::PinnedDrop::drop(pinned_self);
}
}
}
// Automatically create the appropriate conditional `Unpin` implementation.
//
// See ./struct-default-expanded.rs and https://github.com/taiki-e/pin-project/pull/53.
// for details.
pub struct __Struct<'pin, 'a, T> {
__pin_project_use_generics: ::pin_project::__private::AlwaysUnpin<'pin, (T)>,
__field0: T,
__lifetime0: &'a (),
}
impl<'pin, 'a, T> ::pin_project::__private::Unpin for Struct<'a, T> where
__Struct<'pin, 'a, T>: ::pin_project::__private::Unpin
{
}
// A dummy impl of `UnsafeUnpin`, to ensure that the user cannot implement it.
#[doc(hidden)]
unsafe impl<'pin, 'a, T> ::pin_project::UnsafeUnpin for Struct<'a, T> where
__Struct<'pin, 'a, T>: ::pin_project::__private::Unpin
{
}
};
// Implementing `PinnedDrop::drop` is safe, but calling it is not safe.
// This is because destructors can be called multiple times in safe code and
// [double dropping is unsound](https://github.com/rust-lang/rust/pull/62360).
//
// Ideally, it would be desirable to be able to forbid manual calls in
// the same way as `Drop::drop`, but the library cannot do it. So, by using
// macros and replacing them with private traits, we prevent users from
// calling `PinnedDrop::drop`.
//
// Users can implement [`Drop`] safely using `#[pinned_drop]` and can drop a
// type that implements `PinnedDrop` using the [`drop`] function safely.
// **Do not call or implement this trait directly.**
#[doc(hidden)]
impl<T> ::pin_project::__private::PinnedDrop for Struct<'_, T> {
// Since calling it twice on the same object would be UB,
// this method is unsafe.
unsafe fn drop(self: Pin<&mut Self>) {
#[allow(clippy::needless_pass_by_value)]
fn __drop_inner<T>(__self: Pin<&mut Struct<'_, T>>) {
// A dummy `__drop_inner` function to prevent users call outer `__drop_inner`.
fn __drop_inner() {}
**__self.project().was_dropped = true;
}
__drop_inner(self);
}
}
fn main() {}
|
