Macro pin_utils::unsafe_pinned [−][src]
A pinned projection of a struct field.
Safety
To make using this macro safe, three things need to be ensured:
- If the struct implements
Drop
, thedrop
method is not allowed to move the value of the field. - If the struct wants to implement
Unpin
, it has to do so conditionally: The struct can only implementUnpin
if the field’s type isUnpin
. - The struct must not be
#[repr(packed)]
.
Example
use pin_utils::unsafe_pinned; use std::marker::Unpin; use std::pin::Pin; struct Foo<T> { field: T, } impl<T> Foo<T> { unsafe_pinned!(field: T); fn baz(mut self: Pin<&mut Self>) { let _: Pin<&mut T> = self.field(); // Pinned reference to the field } } impl<T: Unpin> Unpin for Foo<T> {} // Conditional Unpin impl
Note: borrowing the field multiple times requires using .as_mut()
to
avoid consuming the Pin
.