RUST

lifetime may not live long enough

fn returns_a_closure(&self,io: IO) -> Box<(dyn Fn() -> u64 + 'static)> {}

convert to:

fn returns_a_closure(&self,io: IO) -> Box<(dyn Fn() -> u64 + '_)> {}

lifetime may not live long enough

fn returns_a_closure(&self,io: IO) -> Box<(dyn Fn() -> u64 + 'static)> {}

convert to:

fn returns_a_closure(&self,io: IO) -> Box<(dyn Fn() -> u64 + '_)> {}