split <;> try split
ε : Type
inst✝ : EventType ε
bound : Time
event : ε
queue₁ queue₂ : Queue ε bound
h : event ∈ queue₂
⊢ event ∈
    if isEmpty queue₁ = true then queue₂
    else
      if isEmpty queue₂ = true then queue₁
      else
        {
          events :=
            merge.mergeImmediate (Array.split queue₁.events fun x => decide (time x = bound)).fst
                (Array.split queue₂.events fun x => decide (time x = bound)).fst ++
              merge.mergeFuture (Array.split queue₁.events fun x => decide (time x = bound)).snd
                (Array.split queue₂.events fun x => decide (time x = bound)).snd,
          sorted :=
            (_ :
              Sorted
                (merge.mergeImmediate (Array.split queue₁.events fun x => decide (time x = bound)).fst
                      (Array.split queue₂.events fun x => decide (time x = bound)).fst ++
                    merge.mergeFuture (Array.split queue₁.events fun x => decide (time x = bound)).snd
                      (Array.split queue₂.events fun x => decide (time x = bound)).snd).data),
          bounded :=
            (_ :
              ∀ {event : ε},
                (merge.mergeImmediate (Array.split queue₁.events fun x => decide (time x = bound)).fst
                          (Array.split queue₂.events fun x => decide (time x = bound)).fst ++
                        merge.mergeFuture (Array.split queue₁.events fun x => decide (time x = bound)).snd
                          (Array.split queue₂.events fun x => decide (time x = bound)).snd)[0]? =
                    some event →
                  bound ≤ time event) }
case inl
ε : Type
inst✝ : EventType ε
bound : Time
event : ε
queue₁ queue₂ : Queue ε bound
h : event ∈ queue₂
h✝ : isEmpty queue₁ = true
⊢ event ∈ queue₂

case inr.inl
ε : Type
inst✝ : EventType ε
bound : Time
event : ε
queue₁ queue₂ : Queue ε bound
h : event ∈ queue₂
h✝¹ : ¬isEmpty queue₁ = true
h✝ : isEmpty queue₂ = true
⊢ event ∈ queue₁

case inr.inr
ε : Type
inst✝ : EventType ε
bound : Time
event : ε
queue₁ queue₂ : Queue ε bound
h : event ∈ queue₂
h✝¹ : ¬isEmpty queue₁ = true
h✝ : ¬isEmpty queue₂ = true
⊢ event ∈
    {
      events :=
        merge.mergeImmediate (Array.split queue₁.events fun x => decide (time x = bound)).fst
            (Array.split queue₂.events fun x => decide (time x = bound)).fst ++
          merge.mergeFuture (Array.split queue₁.events fun x => decide (time x = bound)).snd
            (Array.split queue₂.events fun x => decide (time x = bound)).snd,
      sorted :=
        (_ :
          Sorted
            (merge.mergeImmediate (Array.split queue₁.events fun x => decide (time x = bound)).fst
                  (Array.split queue₂.events fun x => decide (time x = bound)).fst ++
                merge.mergeFuture (Array.split queue₁.events fun x => decide (time x = bound)).snd
                  (Array.split queue₂.events fun x => decide (time x = bound)).snd).data),
      bounded :=
        (_ :
          ∀ {event : ε},
            (merge.mergeImmediate (Array.split queue₁.events fun x => decide (time x = bound)).fst
                      (Array.split queue₂.events fun x => decide (time x = bound)).fst ++
                    merge.mergeFuture (Array.split queue₁.events fun x => decide (time x = bound)).snd
                      (Array.split queue₂.events fun x => decide (time x = bound)).snd)[0]? =
                some event →
              bound ≤ time event) }