Bug 33389 Read-Only files: Quick fix enabled and gets checkmark!
RC1 1. set a file to ready only. 2. Open the file an set the cursor inside 3. Open the 'Edit' menu. Note that 'Quick fix' is enabled, but 'Content assist' is not 4. Choose 'Quick fix' 5. Open the context menu: Quick fix got a checkmark!
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/CompilationUnitEditor.java
* is <code>true</code> the editor's input element is reconciled in advance. If it is 
	 * <code>false</code> this method only returns a result if the editor's input element
	 * does not need to be reconciled.
	 * 
	 * @param offset the offset included by the retrieved element
	 * @param reconcile <code>true</code> if working copy should be reconciled
	 */
	protected IJavaElement getElementAt(int offset, boolean reconcile) {
		IWorkingCopyManager manager= JavaPlugin.getDefault().getWorkingCopyManager();
		ICompilationUnit unit= manager.getWorkingCopy(getEditorInput());
		
		if (unit != null) {
			try {
				if (reconcile) {
					synchronized (unit) {
						unit.reconcile();
					}
					return unit.getElementAt(offset);
				} else if (unit.isConsistent())
					return unit.getElementAt(offset);
					
			} catch (JavaModelException x) {
				JavaPlugin.log(x.getStatus());
				
			}
		}
		
		return null;
	}