if (wc.findPrimaryType() == null) return null;
	private static SearchResultGroup getReferences(ICompilationUnit wc, IProgressMonitor pm) throws JavaModelException{		pm.subTask(RefactoringCoreMessages.getString("CopyRefactoring.searching")); //$NON-NLS-1$		IJavaSearchScope scope= SearchEngine.createJavaSearchScope(new IJavaElement[]{wc});		ISearchPattern pattern= createSearchPattern(wc.findPrimaryType());		SearchResultGroup[] groups= RefactoringSearchEngine.search(pm, scope, pattern, new ICompilationUnit[]{wc});		Assert.isTrue(groups.length <= 1); //just 1 file or none		if (groups.length == 0)			return null;		else				return groups[0];	}