Set: pp::colors
  Set: pp::unicode
  Assumed: f
⊤ + ⊥
10 + 20
10 + - 20
  Set: lean::pp::notation
  Set: lean::pp::coercion
f ⊤ ⊥
Nat::add 10 20
Int::add (nat_to_int 10) (Nat::neg 20)