Token provides uniqueness by relying on object equality, which means that new Token is actually a side-effect in this case.

We want to make sure we preserve referential transparency when using tokens, but imposing a Sync bound is not desirable here, since it forces a very strong constraint on user code for something that is not only an internal implementation detail, but also has zero impact on meaningful behaviour for the user, unlike for example internal concurrency.

Furthermore, token creation has the following properties: - it's synchronous - it's infallible - it's not created in contexts that affect stack safety such as iteration

Given all these reasons, we suspend it via flatMap instead of using Sync[F].delay. Do not try this at home.

Note: The Compiler.Target bound only resolves if F has an instance of Sync or Concurrent, meaning that flatMap is guaranteed to suspend.