Roc Zulip Daily Summary — 2026-02-20

  • Realm: https://roc.zulipchat.com
  • Window: 2026-02-20 12:00 AM to 2026-02-21 12:00 AM (America/Los_Angeles)
  • Messages: 9
  • LLM: vertex_open_model model=zai-org/glm-5-maas topics=3 ok=3/3

Top threads

Roc crashed: Builtin.U8 does not implement len()

Key links

Summary

Lukas Juhrich reported a Roc compiler crash with the error “Builtin.U8 does not implement len()” and asked for guidance on how to debug the issue themselves to learn about the compiler, rather than just obtaining a fix.

Key points

  • The crash occurs in a snippet involving Str.to_utf8, pattern matching on bytes.first(), and a custom take_while function.
  • Anton suggested using AI to fix the bug and running zig build minici for testing, noting that difficult bugs require deep expertise or help from domain experts.
  • Luke Boswell identified that since roc check passes, the bug is likely in the interpreter, not the type checker.
  • Luke recommended creating a snapshot test (zig build snapshot -- path/to/snapshot.md) to narrow down the issue and using zig build roc for faster rebuilds.

Open questions

  • What is the root cause of the “Builtin.U8 does not implement len()” crash?

Action items

  • Create a snapshot test to reproduce the bug and generate human-readable IRs.
  • If the snapshot test doesn’t reproduce it, use the trace-eval flag or print debugging to investigate the interpreter.

.. vs _

Summary

Anton expressed gratitude and appreciation towards Jared Ramirez.

Key points

  • Anton thanked Jared Ramirez for a previous contribution or clarification.
  • The reaction was positive, indicated by the heart emoji.

Open questions

  • None

Action items

  • None

Worklog (Draft PRs and coordination)

Key links

Summary

Anton announced that the Pull Request for implementing file imports is ready for review.

Key points

  • The feature being implemented is file imports, using the syntax import "README.md" as readme : Str.
  • The relevant Pull Request is numbered #9187.

Open questions

  • None

Action items

  • Review PR#9187.