What Herb Stutter misses on his Typescript and Kotlin for C++ metaphor is the actual reality how those languages integrate, unlike cpp2.
Typescript is a linter, nothing else, type annotations for JavaScript. The two features that aren't present in JavaScript, enums and namespaces, are considered design mistakes and the team vouched to focus only on being a linter,and polyfill for older runtimes, when possible (some JS features require runtime support).
While Kotlin spews JVM bytecode many language constructs, like co-routines, make it one way, it is easy to call Java from Kotlin, the other way around requires boilerplate code, manipulating the additional classes generated by the Kotlin compiler for its semantics.