See this:
it appears that the return type from create_static still captures the lifetime of its argument _s, despite being declared as + 'static, and that argument not being used. Which seems odd, especially since if you replace S with &str in args of both alpha and create_static, it works fine (the return type doesn't capture the unnamed lifetime of &str).
What am I missing here, and/or is there a way to use impl Trait in the return position to indicate that the returned impl is 'static?