∀ {α : Type u} {β : α → Type v} (m : Std.DHashMap.Internal.Raw₀ α β) [inst : BEq α] [inst_1 : Hashable α]
  [inst_2 : LawfulBEq α] (h : (↑m).WF) {k a : α} {v : β k} {h₁ : (m.insertIfNew k v).contains a = true},
  (m.insertIfNew k v).get a h₁ = if h₂ : (k == a) = true ∧ m.contains k = false then cast ⋯ v else m.get a ⋯