I use the
/*jslint plusplus: true */
I searched through the
JSLint repo on Github, and couldn't find any mention of a
plusplus option in the current version of
jslint.js. So, I did some digging, and found that the
plusplus option was removed in this commit on May 1, 2015 (it was still present in the previous commit). Here is Crockford's announcement that he'll be removing that option, among others, in his next release.
Therefore, because this option was removed about a year ago, you just won't be able to use it with current versions of JSLint.