Goal:
    A : Type  B : Type  P : A → B → Type  Q : A → B → Type  H : All2 Q [] []
  ============================
   (All2 (Trel_conj P Q) [] [])


DEBUG:Going to execute:
DepElim.is_introduced H; CoreTactics.block_goal;
            CoreTactics.revert_until H; CoreTactics.block_goal