warning: enum is never used: `Void`
  --> $DIR/derive-uninhabited-enum-38885.rs:8:1
   |
LL | enum Void {} //~ WARN never used
   | ^^^^^^^^^
   |
   = note: `-W dead-code` implied by `-W unused`

warning: enum is never used: `Foo`
  --> $DIR/derive-uninhabited-enum-38885.rs:11:1
   |
LL | enum Foo { //~ WARN never used
   | ^^^^^^^^