Generics

Start with the idea

Trait bounds state exactly the capabilities the generic body needs, and the compiler generates a specialised copy per concrete type. That means generics cost nothing at runtime — but a bound wider than necessary narrows who can call you.

Generics let one implementation describe several concrete types without erasing what those types are. In the largest example, T is a placeholder chosen by the caller. The function does not need to know how to print or clone T; it only compares references, so PartialOrd is the capability that matters. A bound is a promise to the compiler about which operations the body may use, and it is a constraint on every caller. Adding Clone because it seems convenient would exclude useful types for no reason.