别针<&mut MaybeUninit<T>> 插入别针<&mut T>

Question

假设

Pin<&mut T>

已初始化，如何从

Pin<&mut MaybeUninit<T>>

安全地获取

MaybeUninit<T>

？

Answer 1

通过

Pin::map_unchecked_mut

应该是安全的：

let pin_uninit_t: Pin<&mut MaybeUninit<T>> = ...;
let pin_t: Pin<&mut T> = unsafe { pin_uninit_t.map_unchecked_mut(|m| m.assume_init_mut()) };