error[E0277]: the trait bound `C: Sealed` is not satisfied
  --> tests/fail/01-general.rs:20:6
   |
20 | impl T for C {}
   |      ^ the trait `Sealed` is not implemented for `C`
   |
note: required by a bound in `T`
  --> tests/fail/01-general.rs:11:1
   |
11 | #[sealed]
   | ^^^^^^^^^ required by this bound in `T`
12 | trait T {}
   |       - required by a bound in this
   = note: this error originates in the attribute macro `sealed` (in Nightly builds, run with -Z macro-backtrace for more info)