isUnliftedTyCon is ill-defined with UnliftedDatatypes

According to Note [Any types] in GHC.Builtin.Types,

  * If (Any k) is the type of a value, it must be a /lifted/ value. So
    if we have (Any @(TYPE rr)) then rr must be 'LiftedRep.  See
    Note [TYPE and RuntimeRep] in GHC.Builtin.Types.Prim.  This is a convenient
    invariant, and makes isUnliftedTyCon well-defined; otherwise what
    would (isUnliftedTyCon Any) be?

This looks wrong.

1. We now have UnliftedDatatypes, which make data T :: TYPE (BoxedRep l) valid. What should isUnliftedTyCon say about T?

2. Is that invariant still valid? There's nothing to verify it as far as I can tell. If not, the comment should be removed.

Perhaps we should remove isUnliftedTyCon in the light of UnliftedDatatypes.