Goal:
    A : Type  B : Type  C : Type  R : A → B → C → Type  b : All3 R [] [] []
  ============================
   (∀ (H := CoreTactics.block) (e : NoConfusionHom_All3 A B C R [] [] []
                                      All3_nil b),
      let H0 := CoreTactics.block in
      noConfusionHom_All3_obligation_2 A B C R [] [] [] All3_nil b
        (noConfusionHom_All3_obligation_1 A B C R [] [] [] All3_nil b e) = e)


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