tests/ui/consts/const-array-oob.rs - toolchain/rustc - Git at Google

 const FOO: [usize; 3] = [1, 2, 3];
 const BAR: usize = FOO[5]; // no error, because the error below occurs before regular const eval

 const BLUB: [u32; FOO[4]] = [5, 6];
 //~^ ERROR evaluation of constant value failed [E0080]
 //~| index out of bounds: the length is 3 but the index is 4

 fn main() {
     let _ = BAR;
 }
	const FOO: [usize; 3] = [1, 2, 3];
	const BAR: usize = FOO[5]; // no error, because the error below occurs before regular const eval

	const BLUB: [u32; FOO[4]] = [5, 6];
	//~^ ERROR evaluation of constant value failed [E0080]
	//~\| index out of bounds: the length is 3 but the index is 4

	fn main() {
	let _ = BAR;
	}