Sure they could. Sum types aren't in go, not because fresh grads can't learn how to use sum types, but because they couldn't see a clean way to add it to go and have it fit with the other stuff they were putting in go, which they thought was more important.
But trying to get new grads to use Haskell on the scale of a 10 million line code base, and have them not make a mess of it? That's the kind of thing he didn't trust the new grads with.
But trying to get new grads to use Haskell on the scale of a 10 million line code base, and have them not make a mess of it? That's the kind of thing he didn't trust the new grads with.