fn get_str() -> &str {
    "Hello World"
}

test.rs:1:17: 1:21 error: missing lifetime specifier [E0106]
test.rs:1 fn get_str() -> &str {
                          ^~~~
test.rs:1:17: 1:21 help: run `rustc --explain E0106` to see a detailed explanation
test.rs:1:17: 1:21 help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
test.rs:1:17: 1:21 help: consider giving it a 'static lifetime
error: aborting due to previous error

fn get_str(s: &str) -> &str {
    "Hello World"
}

fn get_str(s: &str) -> &str

fn get_str<'a>(s: &'a str) -> &'a str

fn get_str() -> &'static str {
    "Hello World"
}