Goal:
  
  A : Type
  B : Type
  R : A → B → Type
  R' : ∀ (a : A) (b : B), R a b → Type
  b : All2_dep R' All2_nil
  ============================
   (∀ (H := CoreTactics.block) (e : NoConfusionHom_All2_dep A B R R' [] []
                                      All2_nil All2_dep_nil b),
      let H0 := CoreTactics.block in
      noConfusionHom_All2_dep_obligation_2 A B R R' [] [] All2_nil
        All2_dep_nil b
        (noConfusionHom_All2_dep_obligation_1 A B R R' [] [] All2_nil
           All2_dep_nil b e) = e)


DEBUG:Going to execute:
fun id =>
             DepElim.generalize_sig id
              ltac:(fun id id' => DepElim.decompose_exists id id')