Free discarded Option and Result payloads

[attahn]

Fresh Option and Result values now release their owned payloads when explicitly discarded. Cleanup covers strings, slices, maps, structs, nested bags, enum errors, and float results while preserving borrowed field and index values.

Focused ASan and LSan tests cover both owned cleanup and borrowed-container safety.

Tested with cargo test --bin mako (78 passed) and the focused ownership sanitizer suite.

Summary by CodeRabbit

• New Features

  • Explicitly discarding Option and Result values now cleans up owned payloads, including nested arrays, maps, strings, and records.
  • Borrowed payloads remain intact so their containing values stay valid.
  • Debug builds warn when a discarded payload’s type cannot be resolved for cleanup.

• Documentation

  • Added guidance for explicit discard syntax and updated soundness and roadmap documentation.

• Tests

  • Added coverage for owned payload cleanup, borrowed values, nested structures, and leak-detection scenarios.

[coderabbitai]

📝 Walkthrough

Walkthrough

Changes

Discarded bag cleanup

Layer / File(s)	Summary
Source type metadata src/codegen/mod.rs	Codegen records source-level function return and struct field types for type-directed cleanup.
Ownership-aware discard emission src/codegen/mod.rs	Ignored Option/Result values now emit recursive cleanup for owned payloads while preserving fallback discard behavior for other values.
Regression coverage examples/testing/*, .github/workflows/ci.yml, src/codegen/mod.rs	Tests cover owned payload shapes, borrowed bags, and an error payload free; ASan runs execute both scenarios.
Documentation updates CHANGELOG.md, docs/*	Documentation describes explicit discard behavior, ownership handling, soundness status, and remaining type-resolution scope.

Estimated code review effort: 4 (Complex) | ~60 minutes

Sequence Diagram(s)

sequenceDiagram
  participant IgnoredStatement
  participant Codegen
  participant GeneratedC
  IgnoredStatement->>Codegen: emit discarded Option/Result expression
  Codegen->>Codegen: infer payload type and ownership
  Codegen->>GeneratedC: emit recursive drop/free cleanup
  GeneratedC-->>IgnoredStatement: complete discard without fallback expression use

Loading

Possibly related PRs

• loreste/mako#6: Both changes update ASan configuration in the CI workflow.

Suggested reviewers: loreste

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 40.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly matches the main change: freeing discarded Option and Result payloads.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}

[attahn]

@coderabbitai review

[coderabbitai]

✅ Action performed

Review finished.

Note: CodeRabbit is an incremental review system and does not re-review already reviewed commits. This command is applicable only when automatic reviews are paused.

[coderabbitai]

🧹 Nitpick comments (1)

.github/workflows/ci.yml (1)

293-296: 🔒 Security & Privacy | 🔵 Trivial | 💤 Low value

Restrict default GITHUB_TOKEN permissions.

The asan job uses default permissions. Following the principle of least privilege, explicitly set read-only permissions to improve workflow security.

🔒️ Proposed fix to explicitly set job permissions

   asan:
     name: ASan invalid memory access
     runs-on: ubuntu-latest
+    permissions:
+      contents: read
     steps:

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In @.github/workflows/ci.yml around lines 293 - 296, Update the asan job
definition to explicitly configure its GITHUB_TOKEN permissions as read-only,
using the workflow’s permissions syntax. Keep the existing job steps and
behavior unchanged.

Source: Linters/SAST tools

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In @.github/workflows/ci.yml:
- Around line 293-296: Update the asan job definition to explicitly configure
its GITHUB_TOKEN permissions as read-only, using the workflow’s permissions
syntax. Keep the existing job steps and behavior unchanged.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: c62c92a9-ae62-4314-b4d4-bba6b648ea20

📥 Commits

Reviewing files that changed from the base of the PR and between 97d1e49 and 5ea0f50.

📒 Files selected for processing (9)

• .github/workflows/ci.yml
• CHANGELOG.md
• docs/ROADMAP.md
• docs/SOUNDNESS.md
• docs/STATUS.md
• docs/howto/06-memory.md
• examples/testing/discarded_bag_borrow_test.mko
• examples/testing/discarded_bag_drop_test.mko
• src/codegen/mod.rs

[attahn]

CI is green except for a macOS timing failure in TestJoinTimeoutFlatten. The same test passed in this run under ASan, UBSan, TSan, GCC, claims, Ubuntu, and Windows, and passed on the upstream base run. I left the unrelated test unchanged; rerunning the failed job requires repository permission.