In most of the cases it was used together with CLASS_ONLY and vice versa
They only case when CLASS_ONLY was used without INNER_CLASS
is possibleParentTargetMap.COMPANION_KEYWORD.
But after diagnostic NESTED_OBJECT_NOT_ALLOWED has been introduced,
there's no sense in the restriction of exactly the companion's parent
For clarification see test data changed
Most of modifier diagnostic is expressed by REDUNDANT_MODIFIER, INCOMPATIBLE_MODIFIERS, REPEATED_MODIFIER, WRONG_MODIFIER_TARGET, WRONG_MODIFIER_PARENT.
A set of modifier diagnostics is not in use now (but not deleted yet).
