Dart is not structurally typed and so only provides help typing the parts of your program you have actually modified to use Dart. TS and Flow both provide stru

Dart is not structurally typed and so only provides help typing the parts of your program you have actually modified to use Dart. TS and Flow both provide structural typing that makes it far easier to convert existing code. Just annotate it (no need to even modify the existing code, just plop a `.d.ts` or `.flow` file in the right place) and immediately start to see benefits.