error: generic parameters may not be used in enum discriminant values
  --> $DIR/issue-67945-2.rs:4:28
   |
LL |     Var = type_ascribe!(0, S),
   |                            ^ cannot perform const operation using `S`
   |
   = note: type parameters may not be used in enum discriminant values

error[E0392]: type parameter `S` is never used
  --> $DIR/issue-67945-2.rs:3:10
   |
LL | enum Bug<S> {
   |          ^ unused type parameter
   |
   = help: consider removing `S`, referring to it in a field, or using a marker such as `PhantomData`
   = help: if you intended `S` to be a const parameter, use `const S: /* Type */` instead

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0392`.