error: unconstrained generic constant
  --> $DIR/trivial-anon-const-use-cases.rs:14:12
   |
LL |     stuff: [u8; { S + 1 }], // `S + 1` is NOT a valid const expression in this context.
   |            ^^^^^^^^^^^^^^^
   |
help: try adding a `where` bound
   |
LL | struct Y<const S: usize> where [(); { S + 1 }]: {
   |                          ++++++++++++++++++++++

error: aborting due to 1 previous error