Some tidbits from what I've read, etc, about Flutter -

They moved to Dart from JavaScript three years ago, after looking at dozen of other languages.

One of the flutter guys posted, the other day, that he had very poor opinion about Dart, just like the rest of the web, until he tried it.

The dev build are JIT and has sub second stateful hot reload feature, which came from Dart. Release build compiles to native code.