message: Fix missing link in `Executor::enter` doc comment
diff: @@ -56,6 +56,8 @@ pub trait Executor: Sized {
  /// before creating futures. This method can be leveraged to set up this
  /// global state, call a function, restore the state, and obtain the result
  /// of the call.
  + ///
  + /// [`Executor`]: trait.Executor.html
  fn enter<R>(&self, f: impl FnOnce() -> R) -> R {
  f()
  }
  