Bug 47838 Make refactoring menu selection sensitive in editor [refactoring]
M5 Currently all refactoring actions are enabled in the editor's context menu. Make them selection dependent. Check if code resolve might be enough (no need to create an AST).
org.eclipse.jdt.ui/ui/org/eclipse/jdt/ui/actions/ChangeTypeAction.java
* <code>
	 * org.eclipse.jface.viewers.IStructuredSelection</code>.
	 * 
	 * @param site
	 *            the site providing context information for this action
	 */
	public ChangeTypeAction(IWorkbenchSite site) {
		super(site);
		setText(RefactoringMessages.getString("ChangeTypeAction.label")); 
		setToolTipText(RefactoringMessages.getString("ChangeTypeAction.tooltipText")); 
		setDescription(RefactoringMessages.getString("ChangeTypeAction.description")); 
		WorkbenchHelp.setHelp(this, IJavaHelpContextIds.CHANGE_TYPE_ACTION);
	}
	/*
	 * (non-Javadoc) Method declared on SelectionDispatchAction
	 */
	public void run(ITextSelection selection) {
		if (!ActionUtil.isProcessable(getShell(), fEditor))
			return;
		try {
			ChangeTypeRefactoring refactoring= createRefactoring(SelectionConverter.getInputAsCompilationUnit(fEditor), selection);
			if (refactoring == null)
				return;
			new RefactoringStarter().activate(refactoring, createWizard(refactoring), getShell(), fDialogMessageTitle, false);
		} catch (CoreException e) {
			ExceptionHandler.handle(e, fDialogMessageTitle, RefactoringMessages.getString("ChangeTypeAction.exception")); 
		}
	}
	/*
	 * (non-Javadoc) Method declared on SelectionDispatchAction