let mid := parted.1
case step
α : Type
inst✝ : Order α
n : Nat
arr : Vec α n
first : Nat
last : Fin n
lt : first < ↑last
parted : { mid // first ≤ ↑mid ∧ mid ≤ last } × Vec α n
eq : partition arr ⟨first, ⋯⟩ last ⋯ = parted
ih₁ : sortedRange (quickSortImpl parted.snd first parted.fst.val.prev) first ↑parted.fst.val.prev
ih₂ :
  sortedRange (quickSortImpl (quickSortImpl parted.snd first parted.fst.val.prev) (↑parted.fst.val + 1) last)
    (↑parted.fst.val + 1) ↑last
this : first < n
i j : Fin n
fi : first ≤ ↑i
ij : i ≤ j
jl : ↑j ≤ ↑last
⊢ (compare (quickSortImpl (quickSortImpl parted.snd first parted.fst.val.prev) (↑parted.fst.val + 1) last)[i]
        (quickSortImpl (quickSortImpl parted.snd first parted.fst.val.prev) (↑parted.fst.val + 1) last)[j]).isLE =
    true
case step
α : Type
inst✝ : Order α
n : Nat
arr : Vec α n
first : Nat
last : Fin n
lt : first < ↑last
parted : { mid // first ≤ ↑mid ∧ mid ≤ last } × Vec α n
eq : partition arr ⟨first, ⋯⟩ last ⋯ = parted
ih₁ : sortedRange (quickSortImpl parted.snd first parted.fst.val.prev) first ↑parted.fst.val.prev
ih₂ :
  sortedRange (quickSortImpl (quickSortImpl parted.snd first parted.fst.val.prev) (↑parted.fst.val + 1) last)
    (↑parted.fst.val + 1) ↑last
this : first < n
i j : Fin n
fi : first ≤ ↑i
ij : i ≤ j
jl : ↑j ≤ ↑last
mid : { mid // first ≤ ↑mid ∧ mid ≤ last } := parted.fst
⊢ (compare (quickSortImpl (quickSortImpl parted.snd first parted.fst.val.prev) (↑parted.fst.val + 1) last)[i]
        (quickSortImpl (quickSortImpl parted.snd first parted.fst.val.prev) (↑parted.fst.val + 1) last)[j]).isLE =
    true