exact absurd ht.symm (ne_of_lt $ lt_of_lt_of_le e.tag_lt e'.tag_le)
α : Type
inst✝ : Proper α
s s₁ s₁✝ s₂✝ s₃✝ : State α
e : s₁✝ ↓ₜ s₂✝
e' : RTC s₂✝ s₃✝
a_ih✝ : ∀ {s₂ : State α}, s₃✝.tag = s₂.tag → RTC s₂✝ s₂ → s₃✝ = s₂
ht : s₃✝.tag = s₁✝.tag
⊢ s₃✝ = s₁✝
no goals