Chris is talking about highlighting-within-highlighting.
In many templating systems, you can have a template with multiple file extensions, and IntelliJ will properly highlight and enable editing in both language scopes. As an example, if you edit Ruby On Rails templates that end in:
some_template.html.erb
then, when you are in the template scope, you get HTML syntax highlighting and completion, and when you are in a scripting scope you get ruby highlighting and a very small amount of code completion.
I know we have something similar for the PCF editor, with embedded Gosu snippets, but this problem is more general: we should be able to detect the language for a given compound file ending, such as .javascript.gst or .xml.gst and support mixing the outer file types content with script components.
I recall looking into this at one point and finding there are two different APIs: one for embedding expressions within a broader context and one for more seamlessly mixing content. The latter API was more difficult, but allows for this extremely nice mixing of languages within a template.
Anyway, Chris, unless you can find a hack work around, it might be a bit before you see this. :)
Cheers,
Carson