Could not create AST on opening AST view

[noopur2507]

package nn;

public class ZZ {
	public void foo(Integer n) {
		switch (n) {
		case Integer x when x.equals(10) -> {
		}
		case Comparable<?> y -> {
		}
		}
		;
	}
}

• Open a Java file with the above code.
• Open AST view.
• The following exception was thrown:

org.eclipse.core.runtime.CoreException: Could not create AST:
Operation only supported in JLS21 AST
	at org.eclipse.jdt.astview.views.ASTView.internalSetInput(ASTView.java:562)
	at org.eclipse.jdt.astview.views.ASTView.refreshAST(ASTView.java:1132)
	at org.eclipse.jdt.astview.views.ASTView.setASTLevel(ASTView.java:1143)
	at org.eclipse.jdt.astview.views.ASTView$ASTLevelToggle.run(ASTView.java:186)
	at org.eclipse.jface.action.Action.runWithEvent(Action.java:474)
	at org.eclipse.jface.action.ActionContributionItem.handleWidgetSelection(ActionContributionItem.java:581)
	at org.eclipse.jface.action.ActionContributionItem.lambda$4(ActionContributionItem.java:415)
	at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:91)
	at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4660)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1657)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1680)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1665)
	at org.eclipse.swt.widgets.Widget.notifyListeners(Widget.java:1394)
	at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4427)
	at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:4003)
	at org.eclipse.e4.ui.workbench.renderers.swt.StackRenderer.showMenu(StackRenderer.java:1436)
	at org.eclipse.e4.ui.workbench.renderers.swt.StackRenderer$1.widgetSelected(StackRenderer.java:859)
	at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:286)
	at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:91)
	at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4660)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1657)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1680)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1665)
	at org.eclipse.swt.widgets.Widget.notifyListeners(Widget.java:1394)
	at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4427)
	at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:4003)
	at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$5.run(PartRenderingEngine.java:1151)
	at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:339)
	at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1042)
	at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:153)
	at org.eclipse.ui.internal.Workbench.lambda$3(Workbench.java:665)
	at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:339)
	at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:573)
	at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:173)
	at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:178)
	at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:208)
	at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:143)
	at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:109)
	at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:439)
	at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:271)
	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
	at java.base/java.lang.reflect.Method.invoke(Method.java:580)
	at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:668)
	at org.eclipse.equinox.launcher.Main.basicRun(Main.java:605)
	at org.eclipse.equinox.launcher.Main.run(Main.java:1481)
	at org.eclipse.equinox.launcher.Main.main(Main.java:1454)

[jukzi]

@noopur2507 there should be a RuntimeException as rootcause, please add its stacktrace

[iloveeclipse]

I can't reproduce (I've tested with Java 21). I assume project compliance is too low.
@akurtakov : related to your latest changes?

[akurtakov]

I will take a look.

[akurtakov]

Just tested in 4.34 and the error happens there so not a regression in this cycle.
What I used to reproduce is have a Java 21 project with the given source file, open the ast view on it, choose ast level 17.
I've tried on Eclipse 4.34 valid java 17 switch expression on Java 11 AST:

package nn;

public class ZZ {
	public enum Day {
		SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY;
	}

	public void foo(Integer n) {
		Day day = Day.MONDAY;
		int numLetters = switch (day) {
        case MONDAY, FRIDAY, SUNDAY -> {
            System.out.println(6);
            yield 6;
        }
        default -> {
            throw new IllegalStateException("Invalid day: " + day);
        }
    };  
	}
}

which led to MethodDeclaration being marked malformed.

Java 21 features seems to not be handled that gracefully.

[akurtakov]

Isssue comes from call of unsupported . Most likely due to supportedOnlyIn19()->supportedOnlyIn20()->supportedOnlyIn21() changes in NullPattern (e.g. eclipse-jdt/eclipse.jdt.core#627) that haven't been accompanied with corresponding ASTConverter adjustment.
I might be able to look into this more once the AST business streamlines a bit.