Lean4
/-- Transfer a `PartialOrder` on `β` to a `PartialOrder` on `α` using an injective
function `f : α → β`.
See also `Function.Injective.partialOrder` when only the proof fields need to be transferred.
See note [reducible non-instances]. -/
abbrev lift [PartialOrder β] (f : α → β) (inj : Injective f) : PartialOrder α :=
letI _instLE : LE α := ⟨fun a b ↦ f a ≤ f b⟩
letI _instLT : LT α := ⟨fun a b ↦ f a < f b⟩
Function.Injective.partialOrder f inj .rfl .rfl