If you have a future `foo: Future[Unit]` and do a `await(foo)` the compiler will give a warning: ``` Warning:(258, 16) a pure expression does nothing in statement position; you may be omitting necessary parentheses await(foo) ^ ``` Edit: This does not happen in all `await`s on `Future[Unit]`s, as I initially assumed. Below is the minimal code I could get that reproduces this: ``` def foo(foobaz: Future[Unit]) = async { if ("".isEmpty) { await(foobaz) 0 } } ```