Running the typechecker independently of the bundler is really common in TypeScript. Typechecking takes time, and blocking on it to transpile and bundle your JS doesn't really add any benefit. Most build systems run the checker in parallel because it cuts down on build time. Plus, Webpack doesn't really do transpiling or typechecking for you — your loaders do. Webpack's loaders can't really check your types because, without doing a lot of extra magic, they operate on one file at a time. If you use Babel with Webpack, for example, Babel just strips out your TypeScript annotations and calls it a day.
All that aside, it seems like Turbopack was literally developed with Webpack's maintainer, who claims it to be a "rust-powered successor to webpack" (his signature is quite literally on the homepage[0]).
All that aside, it seems like Turbopack was literally developed with Webpack's maintainer, who claims it to be a "rust-powered successor to webpack" (his signature is quite literally on the homepage[0]).
[0]:https://turbo.build/pack