Semantic information context menu items should be shown only when applicable

[svick]

In the Syntax Visualizer, when you right-click on a syntax node, a context menu appears that lets you view semantic information about that node. But the context menu is not smart enough to display only the menu items that are applicable. Instead, the text for each item ends with "(if any)":

I think this could be improved and that each of the context menu items should be displayed only if the corresponding semantic information is available.