nt by adding your own code,
or adding your functions to lint's tables, or most simply by defining signatures for your functions.
snd-lint.scm performs these tasks for Snd.  (lint exports its innards via *lint*).
lint is not smart about functions defined outside the current file, so *report-undefined-variables*
sometimes gets confused. You'll sometimes get a recommendation from lint that is less than helpful; nobody's perfect.
If it's actually wrong, and not just wrong-headed, please let me know.
Also in lin