Roc Zulip Daily Summary — 2026-02-19

• Realm: https://roc.zulipchat.com
• Window: 2026-02-19 12:00 AM to 2026-02-20 12:00 AM (America/Los_Angeles)
• Messages: 1
• LLM: vertex_open_model model=zai-org/glm-5-maas topics=1 ok=1/1

Top threads

.. vs _

• Channel: compiler development
• Conversation: .. vs _
• Messages: 1
• People: 1
• Time: 8:31 AM–8:31 AM (America/Los_Angeles)
• Participants: Jared Ramirez
• Link: https://roc.zulipchat.com/#narrow/channel/395097-compiler-development/topic/.2E.2E.20vs.20_/near/574771634

Summary

Jared Ramirez identified that the Rust compiler silently upgrades error type signatures to support “polarity,” a feature not yet implemented in the new compiler, causing issues with Err payload merging.

Key points

• The type signature Result {} [EmptyStrErr] is implicitly upgraded to Result {} [EmptyStrErr]_.
• This implicit upgrade allows error payloads to be mergable when using the ? operator.
• “Polarity” is the name of the feature responsible for this behavior.
• A manual workaround exists to replicate the behavior in the new compiler.

Open questions

• None.

Action items

• Update the type definition of line to Str -> Try({}, [EmptyStrErr, ..]) to fix the merging issue.