Set: pp::colors
  Set: pp::unicode
  Assumed: T
  Assumed: R
  Assumed: t2r
  Coercion t2r
  Assumed: g
  Assumed: a
g a a
  Assumed: b
g a b
g b a
  Set: lean::pp::coercion
g (t2r a) (t2r a)
g (t2r a) b
g b (t2r a)
  Set: lean::pp::coercion
  Assumed: S
  Assumed: s
  Assumed: r
  Assumed: h
  Set: lean::pp::notation
g (g a b) a
h (h r s) r
a ++ b ++ a : R
r ++ s ++ r : S
  Set: lean::pp::coercion
g (g (t2r a) b) (t2r a)
h (h r s) r
  Set: lean::pp::notation
(t2r a) ++ b ++ (t2r a)
r ++ s ++ r