Goal:
  
  A : Type
  P : A → A → Type
  Q : A → Type
  R : A → Type
  hd : A
  tl : list A
  hd' : A
  p : P hd hd'
  X : Q hd
  X0 : All Q tl
  X1 : R hd'
  X2 : All R tl
  ============================
   (Q hd)


DEBUG:Going to execute:
<Coq.Init.Tauto.is_unit_or_eq> flags X1; Ltac.cut X2;
            [ intro; clear id
            | Ltac.cut X1; [ exact id | constructor 1; fail ] ]
Level 0: Backtrace:

R is used in hypothesis X1.
Level 0: Backtrace:

R is used in hypothesis X1.
Level 0: Backtrace:

R is used in hypothesis X1.
Level 0: Backtrace:

R is used in hypothesis X1.
Level 0: Backtrace:

R is used in hypothesis X1.
Level 1: Backtrace:

R is used in hypothesis X1.
Level 0: Backtrace:

R is used in hypothesis X1.
Level 2: Backtrace:

Not convertible.
Level 2: Backtrace:

Not convertible.
Level 2: Backtrace:

Not convertible.
Level 1: Backtrace:

Not convertible.