IAE when opening declared type from link hover

[nlisker]

After #4218 was fixed, the popup menu appears

When selecting Open Declared Type, this exception is thrown:

java.lang.IllegalArgumentException: "&Lhover.Bug4218.Entity<+Ljava.lang.Enum<*>;:Lhover.Bug4218.Index;>;" at 43
	at org.eclipse.jdt.internal.compiler.util.Util.newIllegalArgumentException(Util.java:1577)
	at org.eclipse.jdt.internal.compiler.util.Util.scanTypeSignature(Util.java:1176)
	at org.eclipse.jdt.internal.compiler.util.Util.scanTypeArgumentSignature(Util.java:1503)
	at org.eclipse.jdt.internal.compiler.util.Util.scanTypeArgumentSignatures(Util.java:1467)
	at org.eclipse.jdt.internal.compiler.util.Util.scanClassTypeSignature(Util.java:1368)
	at org.eclipse.jdt.core.Signature.getUnionTypeBounds(Signature.java:1666)
	at org.eclipse.jdt.core.Signature.getUnionTypeBounds(Signature.java:1707)
	at org.eclipse.jdt.internal.ui.javaeditor.JavaElementDeclaredTypeHyperlink.open(JavaElementDeclaredTypeHyperlink.java:139)
	at org.eclipse.jface.text.hyperlink.MultipleHyperlinkPresenter$LinkListInformationControl.openSelectedLink(MultipleHyperlinkPresenter.java:361)
	at org.eclipse.jface.text.hyperlink.MultipleHyperlinkPresenter$LinkListInformationControl$4.mouseUp(MultipleHyperlinkPresenter.java:331)
	at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:262)
	at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:91)
	at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4349)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1217)
	at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4147)
	at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3735)
	at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$5.run(PartRenderingEngine.java:1160)
	at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:339)
	at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1051)
	at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:153)
	at org.eclipse.ui.internal.Workbench.lambda$3(Workbench.java:684)
	at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:339)
	at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:583)
	at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:173)
	at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:185)
	at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:219)
	at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:149)
	at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:115)
	at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:467)
	at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:298)
	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
	at java.base/java.lang.reflect.Method.invoke(Method.java:565)
	at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:615)
	at org.eclipse.equinox.launcher.Main.basicRun(Main.java:563)
	at org.eclipse.equinox.launcher.Main.run(Main.java:1415)

Tested with I20260216-1800 (after the fix for #4218 was merged). The reproducer code is the same.

[srikanth-sankaran]

I'll take a look

[srikanth-sankaran]

No, this is not a regression, but surfaces after #4218 got fixed. I will look into this, though it may be a while as I have other tasks that need attention earlier.