simp_all [Option.isSome_iff_exists]
graph✝ : Graph
cls✝ : Class graph✝
child : Class.Child cls✝
path₁ : Path graph✝ (Class.Child.class child)
h : prefix? (Path.cons child path₁) = none
⊢ ¬Option.isSome (prefix? (Path.cons child path₁)) = true
no goals