Stream: beginners

Topic: Encoding and Decoding tags

view this post on Zulip Erik Karlsson (Nov 22 2025 at 12:08):

Hi,

I seem to be stuck when trying to encode or decode anything that contains a tag, I get

thread '<unnamed>' panicked at crates/compiler/mono/src/ir.rs:6257:10:
Ability specialization is unknown. Tip: check out <https://roc.zulipchat.com/#narrow/stream/231634-beginners/topic/Non-Functions.20in.20Abilities/near/456068617>: DeriveError(Underivable)

When compiling. I've tried both the Json package and Rvn with same result. I'm guessing it's a known issue? Is there any way I can hack around it?

Thanks!

view this post on Zulip Erik Karlsson (Nov 22 2025 at 12:10):

Is there any way I can hack around it?

For the record, what I'm trying to do is send a roc type over the network, both sending and receiving parts are Roc, and the interface between is bytes/List U8

view this post on Zulip Jasper Woudenberg (Nov 22 2025 at 14:10):

Hiya! You're right, this a known limitation of the current decoding setup in the compiler: tags aren't supported yet. There's definitely plans to add support, it just hasn't been implemented yet.

Because of that I also don't have good workarounds, besides limiting yourself to non-taggy-data for the moment.

view this post on Zulip Erik Karlsson (Nov 22 2025 at 14:14):

Okay thanks for the answer! I'll keep a look out for when it lands

Last updated: Nov 28 2025 at 12:16 UTC