error[E0435]: attempt to use a non-constant value in a constant --> $DIR/E0435.rs:5:17 | LL | let _: [u8; foo]; | ^^^ non-constant value | help: consider using `const` instead of `let` | LL | const foo: usize = 42; | ~~~~~ error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0435`.