openScoped.lean:1:8-1:15: error: unknown identifier 'epsilon'
openScoped.lean:4:2-4:24: error: failed to synthesize instance
  Decidable (f = g)
epsilon : {α : Sort u_1} → [h : Nonempty α] → (α → Prop) → α
openScoped.lean:15:8-15:15: error: unknown identifier 'epsilon'
openScoped.lean:20:8-20:15: error: unknown identifier 'epsilon'