Source maps performance

[guybedford]

Traceur has been incredibly quick to parse and write large trees for SystemJS builder. Recently we added source maps support for the full bundling process and this has made compile times about 10x slower, which in some cases has driven builds from under 1 second to close to 10.

We're looking to see how we can improve performance around this, any ideas for where would be best to look here would be much appreciated.

[arv]

Maybe this is another case where we are using indexing into a string rope? Maybe a benchmark would show the problem?

[guybedford]

Sounds like a sensible first step, aiming to get something together next week with some luck.