> Yarn is currently fully covered by Flow types, and to be honest it works pretty well for us - the key part being “us”. Because we want to make it as easy as p

> Yarn is currently fully covered by Flow types, and to be honest it works pretty well for us - the key part being “us”. Because we want to make it as easy as possible for third-party contributors to shim in and help us maintain this awesome tool, we'll switch the codebase to TypeScript. We hope this will help making the codebase feel more familiar than the projects your already contribute to. Seems like Flow works just fine for them, they just want to make it easier for others to contribute.