rw [List.mem_cons] at hy
case pos.left
α : Type
hl : LinearOrder α
inst✝ : DecidableRel LE.le
a x : α
xs : List α
ih : List.Pairwise LE.le xs → List.Pairwise LE.le (insert' a xs)
ordered : List.Pairwise LE.le (x :: xs)
h : a ≤ x
y : α
hy : y ∈ x :: xs
⊢ a ≤ y
case pos.left
α : Type
hl : LinearOrder α
inst✝ : DecidableRel LE.le
a x : α
xs : List α
ih : List.Pairwise LE.le xs → List.Pairwise LE.le (insert' a xs)
ordered : List.Pairwise LE.le (x :: xs)
h : a ≤ x
y : α
hy : y = x ∨ y ∈ xs
⊢ a ≤ y