This is a simplified version of code that I written for a leetcode question. In the problem from leetcode I have an immutable input like aux_vec_i32 below and I need to return something more complicated than in the sample code below, but the compiler errors are similar between the leetcode stuff I wrote and what is below. In the end hmap_for_data should hold the counts of unique counts of items in aux_vec_i32.

The current incantation of ‘&’, ‘mut’, ‘*’ and ‘as’ strewn in the code is the result of me fighting the compiler and not achieving success by following its suggestions.

use std::collections::HashMap;

fn main(){
    struct Data{
        the_data: i32,
    }
    let aux_vec_i32 = vec![1, 2, 3, 1];
    let mut hmap_for_data: HashMap<i32, Data>=HashMap::new();

    for i in &aux_vec_i32 {
        match hmap_for_data.get(&mut aux_vec_i32[*i as usize]) {
            None => {
                hmap_for_data.insert(
                    aux_vec_i32[*i as usize], 
                    Data {
                        the_data: 1,
                    }
                );
            }
            Some(mut data_to_increment) => {
                data_to_increment.the_data += 1;
            }
        }
    }
}

Here is a link to the playground: https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=535206613151ae0e4507296cf816d2a0.