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Your First Compiler PR (guided "safe" changes)

This chapter gives you three starter PRs. Each PR is designed to be:

  • small enough to finish
  • valuable even if you’re new
  • easy to review
  • aligned with the pipeline stages

PR 1 — Add a regression test for a typing rule (Lane A → Lane B bridge)​

Goal: lock in a rule that prevents future regressions.

Steps​

  1. create a minimal .ora file that triggers the diagnostic
  2. add a test expecting that diagnostic
  3. ensure spans point to the right place (if span selection is part of the fix)

Why it’s safe​

  • it strengthens the project without touching core logic first
  • it gives maintainers confidence to accept future refactors

PR 2 — Improve one error message in lowering (Lane A friendly)​

Goal: make one common failure actionable.

What to do​

Pick one lowering error and add:

  • what happened
  • why it happened
  • a “next action” hint (what phase to inspect next)

Why it’s safe​

  • doesn’t change semantics
  • unlocks new contributors
  • improves the product immediately

PR 3 — Add one missing conversion pattern (Lane B starter)​

Goal: fix a concrete “Ora → SIR conversion failed” issue.

What to do​

  1. find the illegal or unsupported op in the emitted MLIR
  2. locate the appropriate conversion pattern directory
  3. add a conversion pattern for the op
  4. add a test proving the conversion now succeeds

Why it’s safe​

  • conversion patterns are localized
  • correctness is visible in the IR
  • tests are easy to write (golden MLIR or “conversion succeeds”)

Review checklist (for all PRs)​

Before you open your PR:

  • Can you explain the issue using the artifact ladder?
  • Did you add a minimal repro file?
  • Did you add or update tests?
  • Does the fix touch the smallest possible phase?

If yes, you’re doing compiler work correctly.