But writing Typescript in Typescript allowed the language-designers to dogfood the developer-experience of being a Typescript-developer. Just like MS eventuall

But writing Typescript in Typescript allowed the language-designers to dogfood the developer-experience of being a Typescript-developer. Just like MS eventually did with C# too. After the C#-compiler was reimplemented in C# (Roslyn), that’s when the language was truly allowed to develop. And it also made it much easier to make C# a truly cross-platform language. When the language-designers don’t have to use their own language, they have objectively much less motivation to improve upon the language or it’s tooling than if they do. The Flow-team didn’t use Flow to write Flow and that shows in its lack of development, its lack of tooling, its lack of contributors and ultimately in its lack of adoption.