I just realized that it's caused by flyCheck rather than elint. Sorry for some misleading information.

I also noticed that elint is unable to identify variables/functions defined in subr.el, startup.el, or any other el files that has no explicit "provides" statement at their end. We may need to add some supplemental information to elint to avoid false-alarms about undefined functions or variables.

Thanks,

Kiong-Gē.