with-only-tag := λ(: tt Type). (: (
   (let rt TAny)
   (match tt (
      ()
      ( (TAnd( lt1 rt1 )) (
         (let lc (with-only-tag lt1))
         (if (non-zero lc) (set rt lc) (
            (let rc (with-only-tag rt1))
            (if (non-zero rc) (set rt rc) ())
         ))
      ))
      ( (TGround( 'Tag_s _ )) (set rt tt) )
      ( _ () )
   ))
   rt
) Type);