1 package checkers.quals; 2 3 import java.lang.annotation.*; 4 5 /** 6 * A meta-annotation to specify all the qualifiers that the given qualifier 7 * is a subtype of. This provides a declarative way to specify the type 8 * qualifier hierarchy. (Alternatively, the hierarchy can be defined 9 * procedurally by subclassing {@link checkers.types.QualifierHierarchy} or 10 * {@link checkers.types.TypeHierarchy}.) 11 * 12 * <p> 13 * Example: 14 * <pre> @SubtypeOf( { Nullable.class } ) 15 * public @interface NonNull { } 16 * </pre> 17 * 18 * <p> 19 * 20 * If a qualified type is a subtype of the same type without any qualifier, 21 * then use <code>Unqualified.class</code> in place of a type qualifier 22 * class. For example, to express that <code>@Encrypted <em>C</em></code> 23 * is a subtype of <code><em>C</em></code> (for every class 24 * <code><em>C</em></code>), and likewise for <code>@Interned</code>, write: 25 * 26 * <pre> @SubtypeOf(Unqualified.class) 27 * public @interface Encrypted { } 28 * 29 * @SubtypeOf(Unqualified.class) 30 * public @interface Interned { } 31 * </pre> 32 * 33 * <p> 34 * 35 * For the root type qualifier in the qualifier hierarchy (i.e., the 36 * qualifier that is a supertype of all other qualifiers in the given 37 * hierarchy), use an empty set of values: 38 * 39 * <pre> @SubtypeOf( { } ) 40 * public @interface Nullable { } 41 * 42 * @SubtypeOf( {} ) 43 * public @interface ReadOnly { } 44 * </pre> 45 * 46 * <p> 47 * Together, all the @SubtypeOf meta-annotations fully describe the type 48 * qualifier hierarchy. 49 * No @SubtypeOf meta-annotation is needed on (or can be written on) the 50 * Unqualified pseudo-qualifier, whose position in the hierarchy is 51 * inferred from the meta-annotations on the explicit qualifiers. 52 */ 53 @Documented 54 @Retention(RetentionPolicy.RUNTIME) 55 @Target(ElementType.ANNOTATION_TYPE) 56 public @interface SubtypeOf { 57 /** An array of the supertype qualifiers of the annotated qualifier **/ 58 Class<? extends Annotation>[] value(); 59 } 60
