Rustで配列の中身をカウントする

use std::collections::HashMap;
fn main() {
    let arr = ['C','C','A','A','B'];
    let mut count: HashMap<char,i32> = HashMap::new();
    for a in arr {
        // println!("{}",a);
        match a {
            'A' =>  {
                let val = count.get(&'A').unwrap_or(&0);
                let val_i32 : i32 = *val;
                count.insert('A', val_i32+1);
            },
            'B' =>  {
                let val = count.get(&'B').unwrap_or(&0);
                let val_i32 : i32 = *val;
                count.insert('B', val_i32+1);
            },
            'C' =>  {
                let val = count.get(&'C').unwrap_or(&0);
                let val_i32 : i32 = *val;
                count.insert('C', val_i32+1);
            },
            _ => {},
        }
    }
    println!("{:?}",count);
}