AndThen missed visit_program pass

[JSerFeng]

If first or second has visit_program, AndThen never reaches there

I wonder if this is intensional or a bug, personally think it is a bug, it this is a bug, I'm willing to fix it

impl<A, B> Fold for AndThen<A, B>
where
    A: Fold,
    B: Fold,
{
    #[inline(always)]
    fn fold_module(&mut self, n: Module) -> Module {
        let n = self.first.fold_module(n);
        self.second.fold_module(n)
    }
    #[inline(always)]
    fn fold_script(&mut self, n: Script) -> Script {
        let n = self.first.fold_script(n);
        self.second.fold_script(n)
    }
}

[JSerFeng]

Can we do something like:

impl<A, B> Fold for AndThen<A, B>
where
    A: Fold,
    B: Fold,
{
    fn fold_program(&mut self, n: Program) -> Program {
        let p = self.first.fold_program(n);
        self.second.fold_program(p)
    }
}