Rust Prevents References From Outliving Their Owners

A reference is only valid while the value it points to still exists. Rust prevents us from returning a reference to a local value that is about to be destroyed in source. The function will not compile:

fn create_message() -> &String {
    let message = String::from("Server started");
    &message
}

message is dropped when the function ends. Returning a reference to it would leave the caller with a reference pointing to invalid memory

Transclude of rust-prevents-dangling-reference

Returning the owned value fixes the problem:

fn create_message() -> String {
    String::from("Server started")
}

Ownership goes back to the caller so the value stays alive