@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@PolyKeyFor has been replaced by @UnknownKeyFor,
one in which every instance of @PolyKeyFor has been
replaced by @KeyForBottom, and ones in which every
instance of @PolyKeyFor has been replaced by @KeyFor, for every possible combination of map arguments.