From daea6d58b56d2facb0476c290a92129c95886b56 Mon Sep 17 00:00:00 2001
From: John Dallaway <john@dallaway.org.uk>
Date: Fri, 13 Oct 2023 09:14:20 +0100
Subject: [PATCH] Do not handle absent external translation units

---
 .../cdt/internal/ui/navigator/OpenCElementAction.java     | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/navigator/OpenCElementAction.java b/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/navigator/OpenCElementAction.java
index 81d5e41f809..1e4b1aba7fd 100644
--- a/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/navigator/OpenCElementAction.java
+++ b/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/navigator/OpenCElementAction.java
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2006, 2008 Wind River Systems, Inc. and others.
+ * Copyright (c) 2006, 2023 Wind River Systems, Inc. and others.
  *
  * This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License 2.0
@@ -11,6 +11,7 @@
  * Contributors:
  *     Anton Leherbauer (Wind River Systems) - initial API and implementation
  *     Ed Swartz (Nokia)
+ *     John Dallaway - do not handle absent external translation units (#563)
  *******************************************************************************/
 package org.eclipse.cdt.internal.ui.navigator;
 
@@ -76,7 +77,10 @@ protected boolean updateSelection(IStructuredSelection selection) {
 				element = ((IAdaptable) element).getAdapter(ICElement.class);
 			}
 			if (element instanceof ICElement && (element instanceof ISourceReference || element instanceof IBinary)) {
-				fOpenElement = (ICElement) element;
+				// do not handle absent external translation units
+				if (!(element instanceof ITranslationUnit tu) || (null != tu.getResource()) || tu.exists()) {
+					fOpenElement = (ICElement) element;
+				}
 			}
 		}
 		return fOpenElement != null || super.updateSelection(selection);