case isFalse =>
  have : ¬(n < m) := by assumption
  have : n < m := prelude_lt_iff_impl_lt.mpr ‹lt n m›
  exact absurd ‹n < m› ‹¬(n < m)›
n m : Nat
x✝ : lt n m
h✝ : ¬n < m
⊢ (if n = m then Ordering.eq else Ordering.gt) = Ordering.lt
no goals