There's a proposal, for what it's worth:
https://github.com/golang/go/issues/57644
Although I'm curious, what is your use case that cannot be fulfilled by interfaces, but can with sum types?
https://github.com/golang/go/issues/57644
Although I'm curious, what is your use case that cannot be fulfilled by interfaces, but can with sum types?
Sum types allow you to express type-level OR. Structs/tuples etc are AND (product types). I like to be able to use both OR and AND at both the expression and type level.