error[E0084]: unsupported representation for zero-variant enum
  --> $DIR/issue-100631.rs:4:1
   |
LL | #[repr(C)]
   | ^^^^^^^^^^
LL | #[repr(C)]
LL | enum Foo {}
   | -------- zero-variant enum

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0084`.