Goal:
  
  A : Type
  B : Type
  R : A → B → Type
  x : A
  y0 : B
  l' : list B
  r : R x y0
  x0 : A
  y : B
  l : list A
  l'0 : list B
  r0 : R x0 y
  a : All2 R l l'0
  ============================
   ({| pr1 := []; pr2 := l' |} = {| pr1 := x0 :: l; pr2 := y :: l'0 |}
    → let H := CoreTactics.block in
      let H0 := CoreTactics.block in ∑ y' : B, y0 :: l' = [y'] × R x y')


DEBUG:Going to execute:
DepElim.simplify_one_dep_elim
Level 2: Backtrace:

Tactic failure (level 1).
Level 1: Backtrace:

Tactic failure.
Level 0: Backtrace:

Tactic failure.