Function hkdf_expand_label_inner

fn hkdf_expand_label_inner<F, T>(
    expander: &dyn HkdfExpander,
    label: &[u8],
    context: &[u8],
    n: usize,
    f: F,
) -> T
where
    F: FnOnce(&dyn HkdfExpander, &[&[u8]]) -> T,