A lot of the focus by the TypeScript team is focused on alignment with the JavaScript language these days and novel new features such as run time types have all

A lot of the focus by the TypeScript team is focused on alignment with the JavaScript language these days and novel new features such as run time types have all but been dismissed or at the very least pushed behind the TC39 JavaScript types proposal. Much like using decorators on variables outside of class structures was. Having said that, TypeScript allows plugins, these are very rarely used as they augment the language by introducing other features that are transformed into the resulting JavaScript files. One plugin that relates to your suggestion of run time types is called Typia, it permits you to use your TypeScript type signatures at runtime with guards like `assert<MyType>(myValue)` where it intercepts the function call to construct an exhaustive if statement in the transpiled JavaScript checking the nature of the passed variable. So while I don't see it being a part of the language in the next four to six years, there are at least libraries out there already that allow you to do it today.