I think he means to make a list of all member of the type and then iterate over it. Then you have the options method that get a union type and can render the correct output

This is mentioned in the article. The author criticizes this because it means they have to keep the type and the list in sync.

I think this is a pretty pedantic reason to dismiss a language, personally.

Maybe to _dismiss_ a language. But it is a reasonable _criticism_ of the language. I hate those kinds of edge cases between strong and weak typing where the compiler knows something, but you have to express it again.

Granted, though, there aren't many languages that can handle that. As far as I can see, it requires compile-time code execution.

IMO that's a pretty good criticism of a language that's supposed to be type-safe, but forces you to break its type safety because its lack of a feature.

And it's not like any other language you can choose from for working in the browser is perfect.