case skip.skip e₁ e₂ =>
  have ha₁ := e₁.indep_allows_iff h.symm |>.mpr e₂.allows_rcn
  have ht₁ := e₁.triggers_iff.not.mpr e₂.not_triggers_rcn
  let s₂' := s₁.record e₂.rcn
  let f₁ : s₁ ↓ₛ s₂' := ⟨ha₁, ht₁⟩
  have ha₂ := f₁.indep_allows_iff h |>.mp e₁.allows_rcn
  have ht₂ := f₁.triggers_iff.not.mp e₁.not_triggers_rcn
  let s₃' := s₂'.record e₁.rcn
  let f₂ : s₂' ↓ₛ s₃' := ⟨ha₂, ht₂⟩
  refine ⟨_, _, .skip f₁, .skip f₂, rfl, rfl, ?_⟩
  exact Step.Skip.comm e₁ e₂ f₁ f₂ rfl rfl |>.symm
α : Type
inst✝ : Proper α
s₁ s₂ s₃ : State α
e₁ : s₁ ↓ₛ s₂
e₂ : s₂ ↓ₛ s₃
h : rcn (skip e₁) ≮[s₁.rtr]≯ rcn (skip e₂)
⊢ ∃ s₂' s₃' e₁' e₂', rcn e₁' = rcn (skip e₂) ∧ rcn e₂' = rcn (skip e₁) ∧ s₃' = s₃
no goals