>>> orbital ~/devtools/arcanist $ arc lint
>>> Lint for src/lint/linter/ArcanistPhutilLibraryLinter.php:

   Error  (PHL1) Unknown Symbol
    Use of unknown class 'BlerpBarp'. Common causes are:

      - Your libphutil/ is out of date.
        This is the most common cause.
        Update this copy of libphutil: /INSECURE/devtools/libphutil

      - Some other library is out of date.
        Update the library this symbol appears in.

      - This symbol is misspelled.
        Spell the symbol name correctly.
        Symbol name spelling is case-sensitive.

      - This symbol was added recently.
        Run `arc liberate` on the library it was added to.

      - This symbol is external. Use `@phutil-external-symbol`.
        Use `grep` to find usage examples of this directive.

    *** ALTHOUGH USUALLY EASY TO FIX, THIS IS A SERIOUS ERROR.
    *** THIS ERROR IS YOUR FAULT. YOU MUST RESOLVE IT.

             181               "*** THIS ERROR IS YOUR FAULT. YOU MUST RESOLVE IT.");
             182
             183             if (false) {
    >>>      184               new BlerpBarp();
             185             }
             186           }
             187         }
>>> orbital ~/devtools/arcanist $