unfold nextTime at h
ε : Type
inst✝ : EventType ε
bound : Time
next : Time.From bound
queue : Queue ε bound
h : nextTime queue = some next
⊢ ∃ event, queue[0]? = some event ∧ time event.val ≥ next.val
ε : Type
inst✝ : EventType ε
bound : Time
next : Time.From bound
queue : Queue ε bound
h :
  (match queue[0]? with
    | none => none
    | some nextEvent => some { val := time nextEvent.val, property := (_ : bound ≤ time nextEvent.val) }) =
    some next
⊢ ∃ event, queue[0]? = some event ∧ time event.val ≥ next.val