has-forward := λ(: tt List<Type>). (: (
   (let return 0_u64)
   (match tt (
      ()
      ( LEOF () )
      ( (LCons( p1 ts )) (
         (set return (max(
            (has-forward( ts ))
            (has-forward( p1 ))
         )))
      ))
   ))
   return
) U64);

has-forward := λ(: tt Type). (: (
   (let return 0_u64)
   (match tt (
      ()
      ( (TGround( 'Array_s ps )) () )
      ( (TGround( 'Cons_s ps )) (set return (has-forward( ps ))) )
      ( (TGround( 'Field_s (LCons( n (LCons( p1 LEOF )) )) )) (set return (has-forward( p1 ))) )
      ( (TGround( cls ps )) (
         (set return (has-forward( ps )))
         (if (not(.lookup( class-exists-index cls 0_u64 ))) (
            (set return 1_u64)
         ) ())
      ))
      ( (TAnd( lt rt )) (
         (set return (max(
            (has-forward( lt ))
            (has-forward( rt ))
         )))
      ))
      ( _ () )
   ))
   return
) U64);