>> What is “foo”? Is it an Identifier or a StringLiteral? > Normally, it's an identifier, since there are no quotes. Sorry, I was vague. I don't mean the seq

>> What is “foo”? Is it an Identifier or a StringLiteral? > Normally, it's an identifier, since there are no quotes. Sorry, I was vague. I don't mean the sequence f o o in the input or the sequence " f o o ". I mean the string (String, str, whatever your language calls it) containing the three letters f o o, which is stored in a union type. Sure, one can lexically-scoped-newtype it if the language supports it, but at that point, unless I'm missing something, it might as well be a sum type.