tests/ui/repr/repr-disallow-on-variant.rs - toolchain/rustc - Git at Google

 struct Test;

 enum Foo {
     #[repr(u8)]
     //~^ ERROR attribute should be applied to an enum
     Variant,
 }

 fn main() {}
	struct Test;

	enum Foo {
	#[repr(u8)]
	//~^ ERROR attribute should be applied to an enum
	Variant,
	}

	fn main() {}