∀ {α : Type u} [inst : BEq α] [inst_1 : Hashable α] {β : Type v} {m₁ m₂ : Std.DHashMap.Raw α fun x => β} [EquivBEq α]
  [LawfulHashable α],
  m₁.WF → m₂.WF → ∀ {k : α} {fallback : β}, k ∉ m₂ → Std.DHashMap.Raw.Const.getD (m₁ ∩ m₂) k fallback = fallback