RFR: 8282483: Ensure that Utils.getAllInterfaces returns unique instances

[Jonathan Gibbons]

On Wed, 2 Mar 2022 16:01:47 GMT, Pavel Rappo <prappo at openjdk.org> wrote:

> Instances of TypeMirror that are equal (TypeMirror::equals), aren't necessarily the same (Types::isSameType). If care is not taken when putting instances of TypeMirror into a set, that set might end up containing the same instances.
> 
> If Utils.getAllInterfaces is called on a type that extends or implements a particular interface multiple times (on different levels of that type's hierarchy), the returned set might contain multiple representations of that interface. For example, I've seen a case where getAllInterfaces that was passed a TypeElement corresponding to java.util.ArrayList returned a set containing 3 instances of TypeMirror corresponding to `java.util.Collection<E>`.
> 
> A bit of archaeology. The old standard doclet (removed in JDK-8177511, commit 33ab1995) collected instances of com.sun.javadoc.Type in a TreeMap, keying them by instances of com.sun.tools.javadoc.main.ClassDocImpl (removed in JDK-8215584, commit 151e628) which implemented Comparable. ClassDocImpl.compareTo worked by comparing instances of CollationKey derived from FQNs of types represented by respective instances of ClassDocImpl.
> 
> I'm not sure why `TreeMap<ClassDocImpl, Type>` was changed to `LinkedHashSet<TypeMirror>`.

src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/toolkit/util/Utils.java line 919:

> 917:             TypeElement e = asTypeElement(t);
> 918:             if (isInterface(e)) {
> 919:                 if ((isPublic(e) || isLinkable(e)) && visited.add(typeUtils.asElement(t))) {

Don't you always want to record you've visited the item, whether or not it is public or linkable?  Would it be better to put the new `&& expr` in the previous `if` expression?

or even `if (isInterface(e) && visited.add(e)) ...`

-------------

PR: https://git.openjdk.java.net/jdk/pull/7659