Why can't I use push_str to resolve strings3 ?

[RHSNOW]

I'd like to implement compose_me use push_str, but as the log shows, I failed.

However, even use func push to push a char 'a' no effect.

Is there anything wrong?
Thanks!

[temanmd]

when you do to_string() here:

fn compose_me(input: &str) -> String {
    ...
    input.to_string().push_str(a);
    ...
}

then you call push_str on a new variable (returned from to_string() func call), not on input one
input is already a String type, you dont have to convert it again, just remove to_string()

Also pls check that type is returned here:

let input = String::from(input);

Its String already