case conv_not h2_phi h2_phi' _ h2_ih =>
  simp only [Holds]
  congr! 1
  exact h2_ih V
D : Type
I : Interpretation D
M : MetaValuation D
E : Env
F F' : Formula
h1 : E.WellFormed
h2_phi h2_phi' : Formula
a✝ : IsConv E h2_phi h2_phi'
h2_ih : ∀ (V : Valuation D), Holds D I V M E h2_phi ↔ Holds D I V M E h2_phi'
V : Valuation D
⊢ Holds D I V M E h2_phi.not_ ↔ Holds D I V M E h2_phi'.not_
no goals