error[E0308]: mismatched types
  --> $DIR/upcast_soundness_bug.rs:59:13
   |
LL |     let p = p as *const dyn Trait<u8, u16>; // <- this is bad!
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `u8`, found `u16`
   |
   = note: expected trait object `dyn Trait<u8, u8>`
              found trait object `dyn Trait<u8, u16>`
   = help: `dyn Trait<u8, u16>` implements `Trait` so you could box the found value and coerce it to the trait object `Box<dyn Trait>`, you will have to change the expected type as well

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0308`.