Syntax coloring problem?

[ezanaga1]

I created a test grammar Test.g4 in a java project under src/main/java, the grammar content is:

grammar Test;

The keyword grammar isn't colored.

In Eclipse error log I found this record with an exception:

eclipse.buildId=4.19.0.I20210303-1800
java.version=16
java.vendor=Oracle Corporation
BootLoader constants: OS=win32, ARCH=x86_64, WS=win32, NL=en_US
Command-line arguments:  -os win32 -ws win32 -arch x86_64 -clean -data file:/c:/workspace/

This is a continuation of log file c:\workspace\.metadata\.bak_0.log
Created Time: 2021-04-25 11:01:36.911
org.eclipse.ui
Error
Sun Apr 25 11:02:23 CEST 2021
Unhandled event loop exception

org.eclipse.core.runtime.AssertionFailedException: assertion failed: 
	at org.eclipse.core.runtime.Assert.isTrue(Assert.java:113)
	at org.eclipse.core.runtime.Assert.isTrue(Assert.java:99)
	at net.certiv.dsl.ui.editor.text.BaseEditStrategy.chkPartition(BaseEditStrategy.java:364)
	at net.certiv.dsl.ui.editor.text.AbstractAutoEditStrategy.customizeDocumentCommand(AbstractAutoEditStrategy.java:1139)
	at org.eclipse.jface.text.TextViewer.customizeDocumentCommand(TextViewer.java:3622)
	at net.certiv.dsl.ui.editor.DslEditor$AdaptedSourceViewer.customizeDocumentCommand(DslEditor.java:443)
	at org.eclipse.jface.text.TextViewer.handleVerifyEvent(TextViewer.java:3660)
	at org.eclipse.jface.text.source.projection.ProjectionViewer.handleVerifyEvent(ProjectionViewer.java:1248)
	at org.eclipse.jface.text.TextViewer$TextVerifyListener.verifyText(TextViewer.java:427)
	at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:277)
	at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:89)
	at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4209)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1043)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1067)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1052)
	at org.eclipse.swt.widgets.Widget.notifyListeners(Widget.java:766)
	at org.eclipse.swt.custom.StyledText.modifyContent(StyledText.java:7402)
	at org.eclipse.swt.custom.StyledText.sendKeyEvent(StyledText.java:8308)
	at org.eclipse.swt.custom.StyledText.doContent(StyledText.java:2512)
	at org.eclipse.swt.custom.StyledText.handleKey(StyledText.java:6075)
	at org.eclipse.swt.custom.StyledText.handleKeyDown(StyledText.java:6106)
	at org.eclipse.swt.custom.StyledText.lambda$1(StyledText.java:5795)
	at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:89)
	at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4209)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1043)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1067)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1052)
	at org.eclipse.swt.widgets.Widget.sendKeyEvent(Widget.java:1094)
	at org.eclipse.swt.widgets.Widget.sendKeyEvent(Widget.java:1090)
	at org.eclipse.swt.widgets.Widget.wmChar(Widget.java:1519)
	at org.eclipse.swt.widgets.Control.WM_CHAR(Control.java:4882)
	at org.eclipse.swt.widgets.Canvas.WM_CHAR(Canvas.java:345)
	at org.eclipse.swt.widgets.Control.windowProc(Control.java:4760)
	at org.eclipse.swt.widgets.Canvas.windowProc(Canvas.java:340)
	at org.eclipse.swt.widgets.Display.windowProc(Display.java:4930)
	at org.eclipse.swt.internal.win32.OS.DispatchMessage(Native Method)
	at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3624)
	at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$5.run(PartRenderingEngine.java:1157)
	at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:338)
	at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1046)
	at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:155)
	at org.eclipse.ui.internal.Workbench.lambda$3(Workbench.java:644)
	at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:338)
	at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:551)
	at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:156)
	at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:152)
	at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:203)
	at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:134)
	at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:104)
	at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:401)
	at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:255)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:78)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:567)
	at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:653)
	at org.eclipse.equinox.launcher.Main.basicRun(Main.java:590)
	at org.eclipse.equinox.launcher.Main.run(Main.java:1461)