show s =
    s.to_str()

assert show(1) == "1"
assert show(True) == "True"
# discard show((x,) -> x)

C = Class {x = Int}
C|C <: Show|.
    to_str(ref(self)) = "<C object: x = \{self::x}>"

c = C.new {x = 1}
assert c.to_str() == "<C object: x = 1>"