. apply String.Iterator.ValidFor.of_eq <;> simp [iv.next.toString, iv.next.pos]
case inr.refine_2
nfa : NFA
saveSize : ℕ
it : String.Iterator
current next : SparseSet nfa.nodes.size
saveSlots : Vec (Array (Option String.Pos)) nfa.nodes.size
lastMatch matched : Option (Array (Option String.Pos))
haystack : String
inv : captureNext.go.Inv nfa it haystack current lastMatch
v : it.Valid
eqs : haystack = it.toString
hemp : next.isEmpty = true
atEnd : ¬it.atEnd = true
h✝ : ¬(current.isEmpty && lastMatch.isSome) = true
hm : lastMatch.isNone = true
explored :
  Option (Array (Option String.Pos)) × SparseSet nfa.nodes.size × Vec (Array (Option String.Pos)) nfa.nodes.size
fst✝ : Option (Array (Option String.Pos))
current' : SparseSet nfa.nodes.size
saveSlots' : Vec (Array (Option String.Pos)) nfa.nodes.size
he :
  exploreεClosure nfa it.pos current (captureNext.initSave saveSize) none saveSlots nfa.start #[] =
    (fst✝, current', saveSlots')
mem_current'_iff : ∀ (i : Fin nfa.nodes.size), i ∈ current' ↔ i ∈ current ∨ ↑i ∈ nfa.εClosure ↑nfa.start
stepped : Option (Array (Option String.Pos)) × SparseSet nfa.nodes.size × Vec (Array (Option String.Pos)) nfa.nodes.size
matched' : Option (Array (Option String.Pos))
next' : SparseSet nfa.nodes.size
saveSlots'' : Vec (Array (Option String.Pos)) nfa.nodes.size
hs : eachStepChar nfa it.curr it.next.i current' next saveSlots' = (matched', next', saveSlots'')
h :
  captureNext.go nfa saveSize it.next next' current.clear saveSlots'' (HOrElse.hOrElse matched' fun x => lastMatch) =
    matched
k : Fin nfa.nodes.size
hk : k ∈ next'
w✝ : ℕ
mem_next_iff :
  ∀ (j : Fin nfa.nodes.size),
    j ∈ next' ↔
      ∃ i', ∃ (x : i' < current'.count), i' < w✝ ∧ ∃ i'' ∈ nfa.charStep (↑current'[i']) it.curr, ↑j ∈ nfa.εClosure i''
i : ℕ
isLt : i < current'.count
left✝ : i < w✝
j : ℕ
step : j ∈ nfa.charStep (↑current'[i]) it.curr
cls : ↑k ∈ nfa.εClosure j
cls' : ↑current'[i] ∈ nfa.εClosure ↑nfa.start
l r' : List Char
iv : String.Iterator.ValidFor l (it.curr :: r') it
startPos : String.Pos := { byteIdx := String.utf8Len l }
⊢ String.Iterator.ValidFor ([it.curr].reverse ++ l.reverse.reverse) r' it.next

case inr.refine_3
nfa : NFA
saveSize : ℕ
it : String.Iterator
current next : SparseSet nfa.nodes.size
saveSlots : Vec (Array (Option String.Pos)) nfa.nodes.size
lastMatch matched : Option (Array (Option String.Pos))
haystack : String
inv : captureNext.go.Inv nfa it haystack current lastMatch
v : it.Valid
eqs : haystack = it.toString
hemp : next.isEmpty = true
atEnd : ¬it.atEnd = true
h✝ : ¬(current.isEmpty && lastMatch.isSome) = true
hm : lastMatch.isNone = true
explored :
  Option (Array (Option String.Pos)) × SparseSet nfa.nodes.size × Vec (Array (Option String.Pos)) nfa.nodes.size
fst✝ : Option (Array (Option String.Pos))
current' : SparseSet nfa.nodes.size
saveSlots' : Vec (Array (Option String.Pos)) nfa.nodes.size
he :
  exploreεClosure nfa it.pos current (captureNext.initSave saveSize) none saveSlots nfa.start #[] =
    (fst✝, current', saveSlots')
mem_current'_iff : ∀ (i : Fin nfa.nodes.size), i ∈ current' ↔ i ∈ current ∨ ↑i ∈ nfa.εClosure ↑nfa.start
stepped : Option (Array (Option String.Pos)) × SparseSet nfa.nodes.size × Vec (Array (Option String.Pos)) nfa.nodes.size
matched' : Option (Array (Option String.Pos))
next' : SparseSet nfa.nodes.size
saveSlots'' : Vec (Array (Option String.Pos)) nfa.nodes.size
hs : eachStepChar nfa it.curr it.next.i current' next saveSlots' = (matched', next', saveSlots'')
h :
  captureNext.go nfa saveSize it.next next' current.clear saveSlots'' (HOrElse.hOrElse matched' fun x => lastMatch) =
    matched
k : Fin nfa.nodes.size
hk : k ∈ next'
w✝ : ℕ
mem_next_iff :
  ∀ (j : Fin nfa.nodes.size),
    j ∈ next' ↔
      ∃ i', ∃ (x : i' < current'.count), i' < w✝ ∧ ∃ i'' ∈ nfa.charStep (↑current'[i']) it.curr, ↑j ∈ nfa.εClosure i''
i : ℕ
isLt : i < current'.count
left✝ : i < w✝
j : ℕ
step : j ∈ nfa.charStep (↑current'[i]) it.curr
cls : ↑k ∈ nfa.εClosure j
cls' : ↑current'[i] ∈ nfa.εClosure ↑nfa.start
l r' : List Char
iv : String.Iterator.ValidFor l (it.curr :: r') it
startPos : String.Pos := { byteIdx := String.utf8Len l }
⊢ nfa.reaches k [it.curr]
case inr.refine_3
nfa : NFA
saveSize : ℕ
it : String.Iterator
current next : SparseSet nfa.nodes.size
saveSlots : Vec (Array (Option String.Pos)) nfa.nodes.size
lastMatch matched : Option (Array (Option String.Pos))
haystack : String
inv : captureNext.go.Inv nfa it haystack current lastMatch
v : it.Valid
eqs : haystack = it.toString
hemp : next.isEmpty = true
atEnd : ¬it.atEnd = true
h✝ : ¬(current.isEmpty && lastMatch.isSome) = true
hm : lastMatch.isNone = true
explored :
  Option (Array (Option String.Pos)) × SparseSet nfa.nodes.size × Vec (Array (Option String.Pos)) nfa.nodes.size
fst✝ : Option (Array (Option String.Pos))
current' : SparseSet nfa.nodes.size
saveSlots' : Vec (Array (Option String.Pos)) nfa.nodes.size
he :
  exploreεClosure nfa it.pos current (captureNext.initSave saveSize) none saveSlots nfa.start #[] =
    (fst✝, current', saveSlots')
mem_current'_iff : ∀ (i : Fin nfa.nodes.size), i ∈ current' ↔ i ∈ current ∨ ↑i ∈ nfa.εClosure ↑nfa.start
stepped : Option (Array (Option String.Pos)) × SparseSet nfa.nodes.size × Vec (Array (Option String.Pos)) nfa.nodes.size
matched' : Option (Array (Option String.Pos))
next' : SparseSet nfa.nodes.size
saveSlots'' : Vec (Array (Option String.Pos)) nfa.nodes.size
hs : eachStepChar nfa it.curr it.next.i current' next saveSlots' = (matched', next', saveSlots'')
h :
  captureNext.go nfa saveSize it.next next' current.clear saveSlots'' (HOrElse.hOrElse matched' fun x => lastMatch) =
    matched
k : Fin nfa.nodes.size
hk : k ∈ next'
w✝ : ℕ
mem_next_iff :
  ∀ (j : Fin nfa.nodes.size),
    j ∈ next' ↔
      ∃ i', ∃ (x : i' < current'.count), i' < w✝ ∧ ∃ i'' ∈ nfa.charStep (↑current'[i']) it.curr, ↑j ∈ nfa.εClosure i''
i : ℕ
isLt : i < current'.count
left✝ : i < w✝
j : ℕ
step : j ∈ nfa.charStep (↑current'[i]) it.curr
cls : ↑k ∈ nfa.εClosure j
cls' : ↑current'[i] ∈ nfa.εClosure ↑nfa.start
l r' : List Char
iv : String.Iterator.ValidFor l (it.curr :: r') it
startPos : String.Pos := { byteIdx := String.utf8Len l }
⊢ nfa.reaches k [it.curr]