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


DEBUG:Going to execute:
cbn[eq_rect_r eq_rect] in hyp