Mutably borrow a hash map inside a loop [duplicate] - rust

Question

This question already has answers here:
Why does this mutable borrow live beyond its scope?
(2 answers)
Closed 8 months ago.
I'd like to mutably borrow a hash map on every iteration of a loop.
I have the following hash map, function, and loop:
use std::collections::HashMap;
fn func<'a>(hash_map: &'a mut HashMap<&'a str, String>) {
unimplimented!();
}
fn loop() {
let mut hash_map = HashMap::new();
let mut i = 0;
while i < 10 {
func(&mut hash_map);
i += 1;
}
}
This will produce the following error on the func(&mut hash_map); line:
cannot borrow `hash_map` as mutable more than once at a time
`hash_map` was mutably borrowed here in the previous iteration of the looprustc(E0499)
main.rs(62, 25): `hash_map` was mutably borrowed here in the previous iteration of the loop
How can I refactor this to be able to mutably borrow the hash map on every iteration of the loop?
I believe I understand Rust's ownership rules enough to understand why this error is happening, just not well enough to fix it.
Note: I know there are better ways to write a loop in Rust, just wanted a very simple loop for this example.

Answer 1

Looks like I was using an unneeded lifetime in the function argument type definition. Instead of hash_map: &'a mut HashMap<&'a str, String>, I could just use hash_map: &mut HashMap<&'a str, String>.
The following code works for me.
use std::collections::HashMap;
use external::func;
fn func<'a>(hash_map: &mut HashMap<&'a str, String>) {
unimplimented!();
}
fn loop() {
let mut hash_map = HashMap::new();
let mut i = 0;
while i < 10 {
func(&mut hash_map);
i += 1;
}
}