[pjmlp]

I should have been a bit more specific, Microsoft could have used any language to build the TypeScript compiler.

They took however the best solution by bootstraping it in JavaScript and using node for the process.

Just correct me if I am wrong.

[yareally]

Looks correct to me and makes the most sense to build the tools in the language TypeScript compiles to. On another note, it would appear they will be adding TypeScript support in the beta[1], which makes me very happy.

[1] https://news.ycombinator.com/item?id=6777360