As the post you are responding to pointed out, String::from converts from a string slice to a String. You didn't do this. Your code fails to compile because it

As the post you are responding to pointed out, String::from converts from a string slice to a String. You didn't do this. Your code fails to compile because it attempts to apply + to two string slices, and that is not implemented. @deathanatos also mentioned that. You might find the Rust book page on Strings helpful: https://doc.rust-lang.org/book/strings.html https://doc.rust-lang.org/book/strings.html