Feature gate: #![feature(map_many_mut)]

This is a tracking issue for the HashMap::get_many{,_unchecked}_mut functions.

Attempts to get mutable references to N values in the map at once.

Public API

// in HashMap

pub fn get_many_mut<Q: ?Sized, const N: usize>(
    &mut self,
    ks: [&Q; N]
) -> [Option<&'_ mut V>; N]
where
    K: Borrow<Q>,
    Q: Hash + Eq;

pub unsafe fn get_many_unchecked_mut<Q: ?Sized, const N: usize>(
    &mut self,
    ks: [&Q; N],
) -> [Option<&'_ mut V>; N]
where
    K: Borrow<Q>,
    Q: Hash + Eq;

Steps / History

• Implementation: Expose get_many_mut and get_many_unchecked_mut to HashMap #94647 and Change signature of get_many_mut APIs hashbrown#562
• Final comment period (FCP)
• Stabilization PR

Unresolved Questions

• Should the return type be instead Result<[Option<&mut V>; N], DuplicateKeys>? Tracking Issue for map_many_mut #97601 (comment) and Tracking Issue for map_many_mut #97601 (comment)
  Tracking Issue for map_many_mut #97601 (comment)
• Having instead a entry-like API? Tracking Issue for map_many_mut #97601 (comment)
  Tracking Issue for map_many_mut #97601 (comment)