It’s for the reason I mentioned before: one of TypeScript’s primary goals is that it generates no runtime code. If you run the TypeScript compiler, it will gene

It’s for the reason I mentioned before: one of TypeScript’s primary goals is that it generates no runtime code. If you run the TypeScript compiler, it will generate exactly the same JavaScript code with the types removed*. Since there is no such JavaScript feature, there will be no such TypeScript feature. I’ll add that writing manual type guards is fairly infrequent, so in practice there’s not a lot to gain here. *Modulo polyfilling newer ES features if you compile for a lower version of the spec.