warning: constant evaluation error: attempt to subtract with overflow
  --> $DIR/const-len-underflow-separate-spans.rs:17:20
   |
17 | const LEN: usize = ONE - TWO;
   |                    ^^^^^^^^^
   |
   = note: #[warn(const_err)] on by default

error[E0080]: constant evaluation error
  --> $DIR/const-len-underflow-separate-spans.rs:17:20
   |
17 | const LEN: usize = ONE - TWO;
   |                    ^^^^^^^^^ attempt to subtract with overflow
   |
note: for constant expression here
  --> $DIR/const-len-underflow-separate-spans.rs:22:12
   |
22 |     let a: [i8; LEN] = unimplemented!();
   |            ^^^^^^^^^

error: aborting due to previous error

If you want more information on this error, try using "rustc --explain E0080"