[aschearer]

TypeScript adds some features planned for Javascript such as classes with inheritance and modules. The thinking is that when these features become standardized your TypeScript code will be valid Javascript. (Or at least as far as those features are concerned.) So in the same vein, why doesn't SASS provide the next generation of CSS functionality? That is, you use the proposed syntax for CSS grids and it transforms that into whatever mess is necessary to emulate it in today's CSS. Later when CSS grid support is available no translation is necessary.

I suppose the answer is because it can't do so in CSS alone and that emulating CSS Grid would require CSS, DOM, and Javascript to be emitted from the compiled SASS script. It would be neat if someone who knew more could confirm my suspicion.

I'm not sure I follow your example regarding CoffeeScript and MVC.