src/test/ui/consts/const-prop-ice2.rs - toolchain/rustc - Git at Google

 // build-fail

 fn main() {
     enum Enum { One=1 }
     let xs=[0;1 as usize];
     println!("{}", xs[Enum::One as usize]); //~ ERROR this operation will panic at runtime
 }
	// build-fail

	fn main() {
	enum Enum { One=1 }
	let xs=[0;1 as usize];
	println!("{}", xs[Enum::One as usize]); //~ ERROR this operation will panic at runtime
	}