I like the idea of abstractions that exist only in the source code and at compile time, and have zero runtime footprint.

How does this compare to Google's Closure compiler and library? Does Svelte's compiler do anything that the Closure compiler cannot? Or how about running the source through a hygienic macro system like sweet.js and feeding the output of that to the Closure compiler?

I ask because I'm skeptical of a new, unproven compiler. Google has been using the Closure compiler on production code for years, and its optimizations are pretty awesome.