apply Nonempty.elim h
α qs : Type
inst✝¹ : DecidableEq α
inst✝ : DecidableEq qs
M : DFA α qs
a✝ : Word { x // x ∈ (toGrammar M).Z }
h : a✝ ∈ Grammar.GeneratedLanguage (toGrammar M)
⊢ a✝ ∈ AcceptedLanguage M
α qs : Type
inst✝¹ : DecidableEq α
inst✝ : DecidableEq qs
M : DFA α qs
a✝ : Word { x // x ∈ (toGrammar M).Z }
h : a✝ ∈ Grammar.GeneratedLanguage (toGrammar M)
⊢ Grammar.Derivation (toGrammar M) [Sum.inl (toGrammar M).start] (Sum.inr <$> a✝) → a✝ ∈ AcceptedLanguage M