intro xs a b ys hays haxs
α : Type u
r : α → α → Prop
inst✝¹ : StrictLinearOrder r
inst✝ : DecidableRel r
β : α → Type v
f : (a : α) → β a → β a → Option (β a)
⊢ ∀ {xs : KVChain r β} {a : α} {b : β a} {ys : KVChain r β} {hays : boundLeft a ys} (haxs : boundLeft a xs),
    mergeWith f xs (KVChain.cons a b ys hays) =
      KVChain.cons a b (mergeWith f xs ys) (_ : boundLeft a (mergeWith f xs ys))
α : Type u
r : α → α → Prop
inst✝¹ : StrictLinearOrder r
inst✝ : DecidableRel r
β : α → Type v
f : (a : α) → β a → β a → Option (β a)
xs : KVChain r β
a : α
b : β a
ys : KVChain r β
hays : boundLeft a ys
haxs : boundLeft a xs
⊢ mergeWith f xs (KVChain.cons a b ys hays) = KVChain.cons a b (mergeWith f xs ys) (_ : boundLeft a (mergeWith f xs ys))