error[E0605]: non-primitive cast: `Kind2` as `u8`
  --> $DIR/issue-88621.rs:11:13
   |
LL |     let _ = Kind2::Foo() as u8;
   |             ^^^^^^^^^^^^^^^^^^ an `as` expression can only be used to convert between primitive types or to coerce to a specific trait object

error: aborting due to previous error

For more information about this error, try `rustc --explain E0605`.