Annotation Type HintUnset
Marks the enum constant that means "nothing was chosen".
An annotation member must declare a default -- Java has no null for one, and a member without a default is mandatory, which would force every attribute to be written. So the default has to name SOME constant, and the only honest one to name is a constant that says nothing.
A hint whose attribute is left at this constant is not written into the build request at all, exactly as an attribute the developer never mentioned is not. The build server then applies its own default, which is where that decision belongs: it is the server's to change, and an annotation that restated it would be a second copy going quietly stale in every app already compiled against it.