[cknitt]

Part of #9074.

Behavioural tests for OCaml-derived features that had little or no coverage:

• gadt_test: a typed evaluator, type witnesses with refined matches, an equality witness, existentials (record, tuple and first-class module payloads), a typed printf, GADTs with @as, @tag and @unboxed, and polymorphic recursion.
• advanced_types_test: polymorphic record fields, explicit polymorphic annotations, constraint, as 'a, #...t patterns, private types, variance, destructive substitution, with module, module type of, higher-order and generative functors, and typed first-class modules.
• extensible_variant_test: inline records with @as, rebinding, indexed extensions, private extensible types, and generative local exceptions.
• Two error-message fixtures: matching a GADT without a locally abstract type, and polymorphic recursion without an annotation.

Fixtures for the bugs found are added by the PRs that fix them.

🤖 Generated with Claude Code

https://claude.ai/code/session_01Kbf3gLMawVgtmiKy3TMBc3

[github-actions]

Changelog

No changelog entry.

Semantic Diff

1 commit · Full page

Test GADTs and other OCaml-derived type and module features

_{78f82ac · cknitt + Claude · Oct 27, 2026, 12:39 UTC}

GADTs, existentials, polymorphic record fields, constraint, private and indexed extensible types, destructive substitution and typed first-class modules had no behavioural tests. Part of #9074.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.66%. Comparing base (beb423d) to head (78f82ac).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #9076      +/-   ##
==========================================
+ Coverage   81.45%   81.66%   +0.20%     
==========================================
  Files         460      460              
  Lines       64645    64645              
==========================================
+ Hits        52657    52792     +135     
+ Misses      11988    11853     -135     

see 14 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[pkg-pr-new]

Open in StackBlitz

rescript

npm i https://pkg.pr.new/rescript@9076

@rescript/belt

npm i https://pkg.pr.new/@rescript/belt@9076

@rescript/darwin-arm64

npm i https://pkg.pr.new/@rescript/darwin-arm64@9076

@rescript/linux-arm64

npm i https://pkg.pr.new/@rescript/linux-arm64@9076

@rescript/linux-x64

npm i https://pkg.pr.new/@rescript/linux-x64@9076

@rescript/runtime

npm i https://pkg.pr.new/@rescript/runtime@9076

@rescript/win32-x64

npm i https://pkg.pr.new/@rescript/win32-x64@9076

commit: 78f82ac

[github-actions]

Developer playground preview: https://rescript-lang.github.io/rescript/dev-playground/?version=pr-9076

[cknitt]

@codex review

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-27T14:21:58.043087Z	3b48492	Manual request

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review" or "@codex security review".

Codex reacts with 👀 while any review is running, comments if it has suggestions, and reacts with 👍 once all reviews finish with no findings.

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Hooray!

Reviewed commit: 3b48492446

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".