error[E0517]: attribute should be applied to a struct
  --> $DIR/repr-simd-on-enum.rs:5:8
   |
LL |   #[repr(simd)]
   |          ^^^^
LL | / enum Aligned {
LL | |     Zero = 0,
LL | |     One = 1,
LL | | }
   | |_- not a struct

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0517`.