Set: pp::colors
  Set: pp::unicode
10 + 20 : ℕ
10 : ℕ
10 - 20 : ℤ
-10
5
15 + 10 - 20 : ℤ
  Assumed: x
  Assumed: n
  Assumed: m
n + m
n + x + m
  Set: lean::pp::coercion
(nat_to_int n) + x + (nat_to_int m) + (nat_to_int 10)
x + (nat_to_int n) + (nat_to_int m) + (nat_to_int 10)
(nat_to_int (n + m + 10)) + x
  Set: lean::pp::notation
Int::add (nat_to_int (Nat::add (Nat::add n m) 10)) x