case inl a_is_z =>
  left
  assumption
α : Type u_1
x z : α
r : α → α → Prop
a : α
a_r_b : r a a
b_r_z : Relation.ReflTransGen r a z
a_is_z : a = z
⊢ a = z ∨ a ≠ z ∧ ∃ y, a ≠ y ∧ r a y ∧ Relation.ReflTransGen r y z
no goals