Stream: ideas

Topic: ADT with one variant

nandi (Dec 31 2025 at 00:22):

I have something like

# Define a Person type that can be encoded as a JSON object
Person := [New({ name : Str, age : U64 })].{
    # Custom encode method for Person - encodes as JSON object
    encode : Person, JsonFormat -> List(U8)
    encode = |self, fmt| {
        # Get the inner record via pattern match
        match self {
            New({ name, age }) => {

I have a dilemma because I don't like naming my variants the same names as my types but if I use something like New, then that is what I have to pattern match on which doesn't feel right either. Anyone have any insights?

Richard Feldman (Dec 31 2025 at 00:27):

I think nominal records work already - do they not?

Richard Feldman (Dec 31 2025 at 00:27):

(basically just omit the tag altogether)

nandi (Dec 31 2025 at 00:28):

Possibly lol Im not sure, can you define methods on nominal records? Sorry for my ignorance, still trying to figure out the diff of what is missing from my mind and what is missing from compiler

nandi (Dec 31 2025 at 00:38):

just filed https://github.com/roc-lang/roc/issues/8834 since there doesn't appear to be a way to construct nominal records

Richard Feldman (Dec 31 2025 at 01:40):

on it!

nandi (Jan 01 2026 at 02:56):

https://github.com/roc-lang/roc/issues/8866 seems related

Last updated: Jun 16 2026 at 16:19 UTC