case zero =>
  intro (_ : 0 + m ≃ 0)
  show 0 ≃ 0 ∧ m ≃ 0
  have : m ≃ 0 := Rel.trans (Rel.symm Addition.zero_add) ‹0 + m ≃ 0›
  exact And.intro Rel.refl ‹m ≃ 0›
ℕ : Type
inst✝² : Core ℕ
inst✝¹ : Induction ℕ
inst✝ : Addition ℕ
n m : ℕ
⊢ 0 + m ≃ 0 → 0 ≃ 0 ∧ m ≃ 0
no goals