Goal:
  
  A : Type
  P : A → Type
  Q : A → Type
  x : A
  l : list A
  X : All (λ x : A, P x × Q x) l
  a : P x
  b : Q x
  a0 : All P l
  b0 : All Q l
  ============================
   (All P (x :: l))


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:

Q is used in hypothesis X.
Level 0: Backtrace:

Q is used in hypothesis X.
Level 0: Backtrace:

Q is used in hypothesis X.
Level 0: Backtrace:

Q is used in hypothesis X.
Level 0: Backtrace:

Q is used in hypothesis X.
Level 1: Backtrace:

Q is used in hypothesis X.
Level 0: Backtrace:

Q is used in hypothesis X.
Level 2: Backtrace:

Not convertible.
Level 2: Backtrace:

Not convertible.
Level 2: Backtrace:

Not convertible.
Level 1: Backtrace:

Not convertible.