In Go, can I declare a Foo, and deserialize into it, but instead of a Foo, it is a Bar? No.

Typescript also doesn't catch cases where metaprograming is used when calling a function. You can put anything you want in there.

Thanks for the pointer to this, but this also makes Crockford's point about the need for a language that does this sort of thing and my point that in order to achieve safety, you need to know about such a package and manually employ the package. The compiler will not help you if you make a mistake in manually employing the package, or if you forget to use it, or if you don't know about it.