Struct nekolib_doc::corro::DormantMutRef

pub struct DormantMutRef<'a, T> { /* private fields */ }

struct Base {
    buf: Vec<String>,
    len: usize, // some other data
}

enum Entry<'a> {
    Occupied(OccupiedEntry<'a>),
    Vacant(VacantEntry),
}
use Entry::Occupied;

struct OccupiedEntry<'a> {
    handle: &'a mut String,
    base: &'a mut Base,
}
struct VacantEntry;

impl Base {
    pub fn new() -> Self { Self { buf: vec![], len: 0 } }
    pub fn entry(&mut self, key: usize) -> Entry {
        match self.buf.get_mut(key) {
            Some(handle) => Occupied(OccupiedEntry { base: self, handle }),
            None => unimplemented!(),
        }
    }
}

error[E0499]: cannot borrow `*self` as mutable more than once at a time
  --> src/lib.rs:26:60
   |
22 |     pub fn entry(&mut self, key: usize) -> Entry {
   |                  - let's call the lifetime of this reference `'1`
23 |         match self.buf.get_mut(key) {
   |               --------------------- first mutable borrow occurs here
24 |             Some(handle) => Occupied(OccupiedEntry { base: self, handle }),
   |                             -------------------------------^^^^-----------
   |                             |                              |
   |                             |                              second mutable borrow occurs here
   |                             returning this value requires that `self.buf` is borrowed for `'1`

References

• https://www.reddit.com/r/rust/comments/11f45re
• https://doc.rust-lang.org/nomicon/lifetime-mismatch.html#improperly-reduced-borrows

Implementations

impl<'a, T> DormantMutRef<'a, T>

pub fn new(t: &'a mut T) -> (&'a mut T, DormantMutRef<'a, T>)

pub unsafe fn awaken(self) -> &'a mut T

pub unsafe fn reborrow(&mut self) -> &'a mut T

pub unsafe fn reborrow_shared(&self) -> &'a T

Trait Implementations

impl<'a, T> Send for DormantMutRef<'a, T>

where &'a mut T: Send,

impl<'a, T> Sync for DormantMutRef<'a, T>

where &'a mut T: Sync,