Goal:
    A : Type  B : Type  C : Type  R : A → B → C → Type
  ============================
   (let H := CoreTactics.block in
    let H0 := CoreTactics.block in
    noConfusionHom_All3_obligation_2 A B C R [] [] [] All3_nil All3_nil
      (noConfusionHom_All3_obligation_1 A B C R [] [] [] All3_nil All3_nil I) =
    I)


DEBUG:Going to execute:
match T with
           | context [ CoreTactics.block ] =>
               change T; CoreTactics.intros_until_block
           end