Reason Go should add enums number 5,132: you’re not left up to runtime checks to verify that an enum value is invalid. You can rely on the type system to do that. It’s all well and good to implement marshallers and unmarshallers that verify that the input is a valid enum value, but that doesn’t stop developers from casting any arbitrary string to your enum type. And then what are you expected to do in your String() method (which doesn’t return an error)? Do you panic? Return “invalid?” Return the string enum value as is, even if it is invalid?

Making it impossible to even produce invalid types is the whole reason why we have a type system. It’s why I prefer Go over an untyped language like Python and JavaScript. So it would be nice if Go supported enums in the type system to get this guarantee.