Fully featured compared to what, exactly? If you say Java I might just have to laugh.
Obviously the compatibility with JS is TypeScript's "killer feature", but it's a killer feature that has very explicit costs you're ignoring for some reason. You cannot have a truly excellent type system while trying to maintain the level of compatibility with a dynamic, weakly typed language that TypeScript does, something that the language team acknowledges themselves[0]. I don't quite see how one can call a deliberately unsound type system "the best".
Obviously the compatibility with JS is TypeScript's "killer feature", but it's a killer feature that has very explicit costs you're ignoring for some reason. You cannot have a truly excellent type system while trying to maintain the level of compatibility with a dynamic, weakly typed language that TypeScript does, something that the language team acknowledges themselves[0]. I don't quite see how one can call a deliberately unsound type system "the best".
0: https://www.typescriptlang.org/docs/handbook/type-compatibil...