Goal:
  
  A : Type
  B : Type
  R : A → B → Type
  R' : ∀ (a : A) (b : B), R a b → Type
  xs : list A
  ys : list B
  a : All2 R xs ys
  a0 : All2_dep R' a
  ============================
   (NoConfusionHom_All2_dep A B R R' xs ys a a0 a0)


DEBUG:Going to execute:
CoreTactics.destruct_sigma id
Level 4: evaluation returns
CoreTactics.destruct_sigma id; destruct id
where
id := a0
of type
constr of type tacvalue