error[E0277]: the trait bound `NotZerocopy: zerocopy::Immutable` is not satisfied
  --> tests/ui-stable/diagnostic-not-implemented-immutable.rs:18:23
   |
18 |     takes_immutable::<NotZerocopy>();
   |                       ^^^^^^^^^^^ the trait `zerocopy::Immutable` is not implemented for `NotZerocopy`
   |
   = note: Consider adding `#[derive(Immutable)]` to `NotZerocopy`
   = help: the following other types implement trait `zerocopy::Immutable`:
             &T
             &mut T
             ()
             *const T
             *mut T
             AU16
             Box<T>
             F32<O>
           and $N others
note: required by a bound in `takes_immutable`
  --> tests/ui-stable/diagnostic-not-implemented-immutable.rs:21:23
   |
21 | fn takes_immutable<T: Immutable>() {}
   |                       ^^^^^^^^^ required by this bound in `takes_immutable`