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221 lines
7.0 KiB
221 lines
7.0 KiB
/*
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* Copyright (c) 2005, 2013, Oracle and/or its affiliates. All rights reserved.
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* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*/
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package javax.lang.model.util;
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import javax.lang.model.element.*;
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import javax.annotation.processing.SupportedSourceVersion;
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import javax.lang.model.SourceVersion;
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import static javax.lang.model.SourceVersion.*;
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/**
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* A scanning visitor of program elements with default behavior
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* appropriate for the {@link SourceVersion#RELEASE_6 RELEASE_6}
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* source version. The <tt>visit<i>XYZ</i></tt> methods in this
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* class scan their component elements by calling {@code scan} on
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* their {@linkplain Element#getEnclosedElements enclosed elements},
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* {@linkplain ExecutableElement#getParameters parameters}, etc., as
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* indicated in the individual method specifications. A subclass can
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* control the order elements are visited by overriding the
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* <tt>visit<i>XYZ</i></tt> methods. Note that clients of a scanner
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* may get the desired behavior be invoking {@code v.scan(e, p)} rather
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* than {@code v.visit(e, p)} on the root objects of interest.
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*
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* <p>When a subclass overrides a <tt>visit<i>XYZ</i></tt> method, the
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* new method can cause the enclosed elements to be scanned in the
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* default way by calling <tt>super.visit<i>XYZ</i></tt>. In this
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* fashion, the concrete visitor can control the ordering of traversal
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* over the component elements with respect to the additional
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* processing; for example, consistently calling
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* <tt>super.visit<i>XYZ</i></tt> at the start of the overridden
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* methods will yield a preorder traversal, etc. If the component
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* elements should be traversed in some other order, instead of
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* calling <tt>super.visit<i>XYZ</i></tt>, an overriding visit method
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* should call {@code scan} with the elements in the desired order.
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*
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* <p> Methods in this class may be overridden subject to their
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* general contract. Note that annotating methods in concrete
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* subclasses with {@link java.lang.Override @Override} will help
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* ensure that methods are overridden as intended.
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*
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* <p> <b>WARNING:</b> The {@code ElementVisitor} interface
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* implemented by this class may have methods added to it in the
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* future to accommodate new, currently unknown, language structures
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* added to future versions of the Java™ programming language.
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* Therefore, methods whose names begin with {@code "visit"} may be
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* added to this class in the future; to avoid incompatibilities,
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* classes which extend this class should not declare any instance
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* methods with names beginning with {@code "visit"}.
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*
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* <p>When such a new visit method is added, the default
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* implementation in this class will be to call the {@link
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* #visitUnknown visitUnknown} method. A new element scanner visitor
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* class will also be introduced to correspond to the new language
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* level; this visitor will have different default behavior for the
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* visit method in question. When the new visitor is introduced, all
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* or portions of this visitor may be deprecated.
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*
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* @param <R> the return type of this visitor's methods. Use {@link
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* Void} for visitors that do not need to return results.
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* @param <P> the type of the additional parameter to this visitor's
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* methods. Use {@code Void} for visitors that do not need an
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* additional parameter.
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*
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* @author Joseph D. Darcy
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* @author Scott Seligman
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* @author Peter von der Ahé
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*
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* @see ElementScanner7
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* @see ElementScanner8
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* @since 1.6
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*/
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@SupportedSourceVersion(RELEASE_6)
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public class ElementScanner6<R, P> extends AbstractElementVisitor6<R, P> {
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/**
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* The specified default value.
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*/
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protected final R DEFAULT_VALUE;
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/**
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* Constructor for concrete subclasses; uses {@code null} for the
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* default value.
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*/
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protected ElementScanner6(){
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DEFAULT_VALUE = null;
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}
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/**
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* Constructor for concrete subclasses; uses the argument for the
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* default value.
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*
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* @param defaultValue the default value
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*/
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protected ElementScanner6(R defaultValue){
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DEFAULT_VALUE = defaultValue;
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}
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/**
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* Iterates over the given elements and calls {@link
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* #scan(Element, Object) scan(Element, P)} on each one. Returns
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* the result of the last call to {@code scan} or {@code
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* DEFAULT_VALUE} for an empty iterable.
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*
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* @param iterable the elements to scan
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* @param p additional parameter
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* @return the scan of the last element or {@code DEFAULT_VALUE} if no elements
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*/
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public final R scan(Iterable<? extends Element> iterable, P p) {
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R result = DEFAULT_VALUE;
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for(Element e : iterable)
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result = scan(e, p);
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return result;
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}
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/**
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* Processes an element by calling {@code e.accept(this, p)};
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* this method may be overridden by subclasses.
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*
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* @param e the element to scan
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* @param p a scanner-specified parameter
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* @return the result of visiting {@code e}.
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*/
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public R scan(Element e, P p) {
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return e.accept(this, p);
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}
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/**
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* Convenience method equivalent to {@code v.scan(e, null)}.
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*
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* @param e the element to scan
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* @return the result of scanning {@code e}.
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*/
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public final R scan(Element e) {
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return scan(e, null);
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}
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/**
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* {@inheritDoc} This implementation scans the enclosed elements.
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*
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* @param e {@inheritDoc}
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* @param p {@inheritDoc}
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* @return the result of scanning
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*/
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public R visitPackage(PackageElement e, P p) {
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return scan(e.getEnclosedElements(), p);
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}
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/**
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* {@inheritDoc} This implementation scans the enclosed elements.
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*
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* @param e {@inheritDoc}
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* @param p {@inheritDoc}
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* @return the result of scanning
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*/
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public R visitType(TypeElement e, P p) {
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return scan(e.getEnclosedElements(), p);
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}
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/**
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* {@inheritDoc}
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*
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* This implementation scans the enclosed elements, unless the
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* element is a {@code RESOURCE_VARIABLE} in which case {@code
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* visitUnknown} is called.
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*
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* @param e {@inheritDoc}
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* @param p {@inheritDoc}
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* @return the result of scanning
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*/
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public R visitVariable(VariableElement e, P p) {
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if (e.getKind() != ElementKind.RESOURCE_VARIABLE)
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return scan(e.getEnclosedElements(), p);
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else
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return visitUnknown(e, p);
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}
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/**
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* {@inheritDoc} This implementation scans the parameters.
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*
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* @param e {@inheritDoc}
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* @param p {@inheritDoc}
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* @return the result of scanning
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*/
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public R visitExecutable(ExecutableElement e, P p) {
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return scan(e.getParameters(), p);
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}
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/**
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* {@inheritDoc} This implementation scans the enclosed elements.
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*
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* @param e {@inheritDoc}
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* @param p {@inheritDoc}
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* @return the result of scanning
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*/
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public R visitTypeParameter(TypeParameterElement e, P p) {
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return scan(e.getEnclosedElements(), p);
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}
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}
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