I assume it's derived from the OCaml generic type syntax (the first Rust compiler was written in OCaml after all), for example the definition of the type `Optio

I assume it's derived from the OCaml generic type syntax (the first Rust compiler was written in OCaml after all), for example the definition of the type `Option.t` in OCaml: type 'a t = 'a option = | None | Some of 'a I think this is the case because IIRC this function: fn slice<'a>(s: &'a str) -> &'a str { &s[0..2] } Is generic over the lifetime of `s`, and it I assume it would have been difficult to distinguish generic types and lifetimes.