Fix Class.getSuperClass() infinite loop when called on java.lang.Object

[Copilot]

addDefaultSuperClass() unconditionally assigned java.lang.Object as the default superclass for any class without an explicit extends clause — including java.lang.Object itself — causing getSuperClass() to return Object for Object, producing an infinite loop when traversing the hierarchy transitively.

Change

• JavaModelCompletion.addDefaultSuperClass(): Guard the default superclass assignment with a check against isJavaLangObject(), so java.lang.Object is never given a synthetic self-referential superclass.

// Before
if (javaClass.getExtends() == null && javaClass.getDefaultExtends() == null) {

// After
if (javaClass.getExtends() == null && javaClass.getDefaultExtends() == null
        && !javaClass.isJavaLangObject(javaClass)) {

java.lang.Object.getSuperClass() now returns null, correctly terminating transitive superclass traversal.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Fix Class.getSuperClass() not to return Object for Object</issue_title>
<issue_description>getSuperclass() returns Object if a Class does not declare any concrete extension. This is also done for the class Object.

This may result in an endless loop when transitively traversing getSuperclass()
</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Fix Class.getSuperClass() not to return Object for Object #8

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