Thu, 07 Nov 2013 20:11:56 -0800
8027730: Fix release-8 type visitors to support intersection types
Reviewed-by: jjg, jlahoda, sogoel
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24 */
26 package javax.lang.model.util;
28 import javax.annotation.processing.SupportedSourceVersion;
29 import javax.lang.model.SourceVersion;
30 import javax.lang.model.type.*;
31 import static javax.lang.model.SourceVersion.*;
33 /**
34 * A visitor of types based on their {@linkplain TypeKind kind} with
35 * default behavior appropriate for the {@link SourceVersion#RELEASE_8
36 * RELEASE_8} source version. For {@linkplain
37 * TypeMirror types} <tt><i>XYZ</i></tt> that may have more than one
38 * kind, the <tt>visit<i>XYZ</i></tt> methods in this class delegate
39 * to the <tt>visit<i>XYZKind</i></tt> method corresponding to the
40 * first argument's kind. The <tt>visit<i>XYZKind</i></tt> methods
41 * call {@link #defaultAction defaultAction}, passing their arguments
42 * to {@code defaultAction}'s corresponding parameters.
43 *
44 * <p> Methods in this class may be overridden subject to their
45 * general contract. Note that annotating methods in concrete
46 * subclasses with {@link java.lang.Override @Override} will help
47 * ensure that methods are overridden as intended.
48 *
49 * <p> <b>WARNING:</b> The {@code TypeVisitor} interface implemented
50 * by this class may have methods added to it in the future to
51 * accommodate new, currently unknown, language structures added to
52 * future versions of the Java™ programming language.
53 * Therefore, methods whose names begin with {@code "visit"} may be
54 * added to this class in the future; to avoid incompatibilities,
55 * classes which extend this class should not declare any instance
56 * methods with names beginning with {@code "visit"}.
57 *
58 * <p>When such a new visit method is added, the default
59 * implementation in this class will be to call the {@link
60 * #visitUnknown visitUnknown} method. A new type kind visitor class
61 * will also be introduced to correspond to the new language level;
62 * this visitor will have different default behavior for the visit
63 * method in question. When the new visitor is introduced, all or
64 * portions of this visitor may be deprecated.
65 *
66 * <p>Note that adding a default implementation of a new visit method
67 * in a visitor class will occur instead of adding a <em>default
68 * method</em> directly in the visitor interface since a Java SE 8
69 * language feature cannot be used to this version of the API since
70 * this version is required to be runnable on Java SE 7
71 * implementations. Future versions of the API that are only required
72 * to run on Java SE 8 and later may take advantage of default methods
73 * in this situation.
74 *
75 * @param <R> the return type of this visitor's methods. Use {@link
76 * Void} for visitors that do not need to return results.
77 * @param <P> the type of the additional parameter to this visitor's
78 * methods. Use {@code Void} for visitors that do not need an
79 * additional parameter.
80 *
81 * @see TypeKindVisitor6
82 * @see TypeKindVisitor7
83 * @since 1.8
84 */
85 @SupportedSourceVersion(RELEASE_8)
86 public class TypeKindVisitor8<R, P> extends TypeKindVisitor7<R, P> {
87 /**
88 * Constructor for concrete subclasses to call; uses {@code null}
89 * for the default value.
90 */
91 protected TypeKindVisitor8() {
92 super(null);
93 }
95 /**
96 * Constructor for concrete subclasses to call; uses the argument
97 * for the default value.
98 *
99 * @param defaultValue the value to assign to {@link #DEFAULT_VALUE}
100 */
101 protected TypeKindVisitor8(R defaultValue) {
102 super(defaultValue);
103 }
105 /**
106 * This implementation visits an {@code IntersectionType} by calling
107 * {@code defaultAction}.
108 *
109 * @param t {@inheritDoc}
110 * @param p {@inheritDoc}
111 * @return the result of {@code defaultAction}
112 */
113 @Override
114 public R visitIntersection(IntersectionType t, P p) {
115 return defaultAction(t, p);
116 }
117 }