Function macroexpand

pub(crate) fn macroexpand<'ob>(
    form: &Rt<Slot<Gc<ObjectType<'_>>>>,
    environment: Option<&Rt<Slot<Gc<ObjectType<'_>>>>>,
    cx: &'ob mut Context<'_>,
    env: &mut Rt<Env<'_>>,
) -> Result<Gc<ObjectType<'ob>>>