/// Without this second table, what would happen in a case like
/// this is that we would instantiate `?1` with a generalized
/// type like `Box<?6>`. We would then relate `Box<?3> <: Box<?6>`
/// Without this second table, what would happen in a case like
/// this is that we would instantiate `?1` with a generalized
/// type like `Box<?6>`. We would then relate `Box<?3> <: Box<?6>`