@Documented @PolymorphicQualifier(value=UnknownKeyFor.class) @Retention(value=RUNTIME) @Target(value={TYPE_USE,TYPE_PARAMETER}) public @interface PolyKeyFor
Any method written using @PolyKeyFor conceptually has an arbitrary number of versions:
one in which every instance of @PolyKeyFor has been replaced by @UnknownKeyFor, one in which every instance of @PolyKeyFor has been replaced by
@KeyForBottom, and ones in which every instance of @PolyKeyFor has been
replaced by @KeyFor, for every possible combination of map arguments.