For what it's worth, Dart's intended domain (client UI apps) is much farther from compilers than Go's intended domain (servers and "systems programming") but we write almost all of our tools and compilers in Dart.

Dart isn't always the best language for compilers (we have a lot of Visitor patterns floating around, which are always tedious), but it's plenty good enough and it keeps the whole team working in our own language eight hours a day, which I think is invaluable.

Also, it means that when we make our implementations or compilers faster, we get a compounding effect because our tools get faster too.