Goal:
    hd : A.t  tl : t  X : lt_ tl tl  IHX : False
  ============================
   (let H := CoreTactics.block in let H0 := CoreTactics.block in False)


DEBUG:Going to execute:
change T; CoreTactics.intros_until_block
Level 3: T
 has value 
(let H := CoreTactics.block in False)