Lifetime issue with linked_hash_map iter_mut where there is none with hash_map iter_mut

[mattmacy]

The following code works without issue: https://is.gd/BIFxdX

However, when I comment out the hash_map usage and uncomment the linked_hash_map code - which is verbatim the same AFAICT- it can't resolve the lifetime of iter_mut

[dtolnay]

Reduced:

#[cfg(not(feature = "linked-hash-map"))]
use std::collections::hash_map::{HashMap as Map, IterMut};

#[cfg(feature = "linked-hash-map")]
extern crate linked_hash_map;
#[cfg(feature = "linked-hash-map")]
use linked_hash_map::{LinkedHashMap as Map, IterMut};

fn f<'a, 'r>(m: &'r mut Map<&'a (), ()>) -> IterMut<'r, &'r (), ()> {
    m.iter_mut()
}

fn main() {}

[dtolnay]

Looks like a linked-hash-map bug. Relevant code from libstd that makes this work:

• IterMut
• RawBuckets
• RawBucket

[mattmacy]

¯_(ツ)_/¯