Rust: What is the difference between AsRef and Borrow?

AsRef — cheap reference conversion. Borrow — semantic borrowing.

AsRef:

• For reference conversion.
• No semantic requirements.
• More general.

Borrow:

• Hash/Eq must match.
• Semantic borrowing.
• Used with HashMap.

1fn print_ref<T: AsRef<str>>(s: T) {
2    println!("{}", s.as_ref());
3}
4
5fn get_value<T: Borrow<str>, K: Borrow<T>>(map: &HashMap<K, String>, key: K) -> &String {
6    map.get(key.borrow()).unwrap()
7}

Key: AsRef for general conversion, Borrow for HashMap keys.