case not_ phi phi_ih =>
  unfold NotFree at h1
  unfold IsNotFree at phi_ih
  unfold IsNotFree
  intro V d
  simp only [Holds]
  congr! 1
  exact phi_ih h1 V d
D : Type
I : Interpretation D
M : MetaValuation D
E : Env
Γ : List (VarName × MetaVarName)
v : VarName
h2 : ∀ (X : MetaVarName), (v, X) ∈ Γ → IsNotFree D I M E (meta_var_ X) v
phi : Formula
phi_ih : NotFree Γ v phi → IsNotFree D I M E phi v
h1 : NotFree Γ v phi.not_
⊢ IsNotFree D I M E phi.not_ v
no goals