Goal:
    A : Type  t' : A  P : A → A → Type  hd : A  tl : list A  p : P hd t'
  ============================
   (hd = t')


DEBUG:Going to execute:
F x2 x1 x0
Level 0: Backtrace:

P is used in hypothesis p.
Level 0: Backtrace:

P is used in hypothesis p.
Level 0: Backtrace:

P is used in hypothesis p.
Level 0: Backtrace:

P is used in hypothesis p.
Level 0: Backtrace:

P is used in hypothesis p.
Level 1: Backtrace:

P is used in hypothesis p.
Level 0: Backtrace:

P is used in hypothesis p.