Rust エラー「error[E0369]: cannot add String to &str」が発生した場合の対処法

fn main() {

    let str1: &str = "aaa";
    let str2: String = "bbb".to_string();

    println!( "{}", str1 + str2 );
    
}

error[E0369]: cannot add `String` to `&str`
 --> sample.rs:6:26
  |
6 |     println!( "{}", str1 + str2 );
  |                     ---- ^ ---- String
  |                     |    |
  |                     |    `+` cannot be used to concatenate a `&str` with a `String`
  |                     &str
  |
help: create an owned `String` on the left and add a borrow on the right
  |
6 |     println!( "{}", str1.to_owned() + &str2 );
  |                         +++++++++++   +

error: aborting due to previous error

fn main() {

    let str1: &str = "aaa";
    let str2: String = "bbb".to_string();

    println!( "{}", str1.to_owned() + &str2 );
    // aaabbb
    
}