9.10.3.1 Warnings about style issues with predicates

--warn-dead-predicates

--warn-dead-preds

Warn about predicates and functions that have no procedures which are ever called.

--warn-dead-procedures

--warn-dead-procs

Warn about procedures which are never called.

--warn-can-fail-function

Warn about functions that can fail. (Such functions should be replaced by semidet predicates.)

--no-warn-unneeded-mode-specific-clause

Do not warn about clauses that unnecessarily specify the modes of their arguments.