Error code E0665
Note: this error code is no longer emitted by the compiler.
The Default
trait was derived on an enum.
Erroneous code example:
#![allow(unused)] fn main() { #[derive(Default)] enum Food { Sweet, Salty, } }
The Default
cannot be derived on an enum for the simple reason that the
compiler doesn't know which value to pick by default whereas it can for a
struct as long as all its fields implement the Default
trait as well.
If you still want to implement Default
on your enum, you'll have to do it "by
hand":
#![allow(unused)] fn main() { enum Food { Sweet, Salty, } impl Default for Food { fn default() -> Food { Food::Sweet } } }