Looks like a negative long example slipped in (longs can't be negative).

Where is this stated?
I've found no documentation that longs couldn't be negative,
looking in the code it uses the long type from java, which supports negative numbers,
and testing it, both release- and git-version supports/allows negative long.

Furthermore if longs cannot be negative the changes from jolie/jolie#524 adds the wrong behavior for minimum long value.

Whoops my bad, I got this confused with another project where long stood for unsigned long. Please ignore my last comment.