revert xs
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)
d : α
xs ys : KVChain r β
⊢ boundLeft d xs → boundLeft d ys → boundLeft d (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)
d : α
ys : KVChain r β
⊢ ∀ {xs : KVChain r β}, boundLeft d xs → boundLeft d ys → boundLeft d (mergeWith f xs ys)