obtain rfl | h := eq_or_ne t v <;> obtain rfl | h' := eq_or_ne t u <;>
  (try have := h'.symm) <;> simp [*]
V : Type u
V' : Type v
V'' : Type w
G : Digraph V
G' : Digraph V'
G'' : Digraph V''
t u v w : V
p : Walk G u v
p' : Walk G v w
⊢ t = u ∨ t ∈ List.tail (support p) ∨ t ∈ List.tail (support p') ↔
    (t = u ∨ t ∈ List.tail (support p)) ∨ t = v ∨ t ∈ List.tail (support p')
no goals