Hacktoberfest 2026:メンテナが10月に向けて印を付けた、オープンで初心者向けの issue。 Hacktoberfest の issue を見る

Port selected upstream OCaml type checker improvements (post 4.06)

オープン
#9,130 コメント 1 件 リアクション 0 件 担当者 0 名 GitHub で見る

メンテナーはふだん 1 日以内に返信

まだ誰も着手していません。

評価

難易度
5/5
見積もり時間
1週間以上
初心者へのやさしさ
35/100
issue の種類
機能追加
明瞭さ
おおむね明確
活発さ
活発
技術スタック
ocaml
領域
compilers

調査の方向性

Start by reading the compiler sources under compiler/ml and compare the listed upstream changes with the specific behavior you want to port. The issue asks for each candidate to be a separate PR with tests and a changelog fragment; choose one candidate and use its stated files, such as includecore/includemod for diff-based inclusion errors. Done means the selected improvement is ported and covered by tests, with a changelog fragment.

索引モデルが issue の本文から書いたものです。

説明

The type checker and pattern-match compiler in compiler/ml are a 4.06-era fork of OCaml. They have diverged a lot since then. Upstream has made several improvements in the meantime that would help ReScript users directly. This issue tracks the ones worth porting by hand. A full resync is not a goal.

Candidates, by value

  • Diff-based inclusion errors (4.13, Diffing). Signature mismatches name the record field or variant constructor that was added, removed, swapped or renamed, and the same goes for functor arguments. Today we print "Their kinds differ" or "Fields number N have different names". .resi mismatches are common, and the change stays mostly within includecore/includemod. It needs a port by hand, because of our own error cases (Field_optional, Runtime_annotation, Not_undefined, …).
  • Shapes (4.14). .cmt files record where each definition comes from, through functor applications, include and module aliases. This would remove the analysis limitation for cross-file references through applied functors (see #9084). It is also the basis for project-wide find-references. Requires a cmt format change.
  • Matching on mutable fields under guards (upstream ocaml/ocaml#7241, unsound). We are affected: a failed guard that changes a mutable field can make switch take a case that does not match. Repro and details in #9129. Upstream fixed it in OCaml 5.3 (ocaml/ocaml#13138, ocaml/ocaml#13152).
  • Warning names (4.12). Accept names like +unused-var next to numbers in -w and in rescript.json. Cheap to add, and warning configs become readable.
  • Parmatch improvements. These can be picked one at a time. Counterexamples mention guarded clauses ("some guarded clause may match this value"). Unused cases inside or-patterns are detected more precisely. Refutation is faster.
  • Structured unification traces (Errortrace, 4.14/5.0). These separate unification, equality and moregen failures, which gives more precise "not compatible" explanations. We have already rewritten many messages (error_message_utils), so the gain is smaller and touches more code.
  • Type scopes (4.08–4.11). Escape checks for locally abstract types and first-class modules would use a separate scope instead of levels. This is invasive (ctype/typecore), so only worth it if escape bugs come up.
  • GADT soundness fixes (injectivity, 4.12, and others). Port these when a bug report needs one. GADTs are rare in ReScript code.

Out of scope

  • Abstract type_expr (4.14) and the with_local_level refactor (5.1): a lot of churn, no user-visible gain.
  • Upstream error rendering (Location.report): we have our own code_frame.
  • Lambda/Simplif optimisations and Flambda: the JS backend has its own Lam passes.
  • Language features that don't fit ReScript: binding operators, labeled tuples, effects, unboxed layouts and modes, with module type.
  • Alerts ([@alert]): would only be nice to have unless there is demand for categories beyond @deprecated.

Each checked item should be its own PR with tests and a changelog fragment where users can see the change.

主要言語
OCaml
スター
7.5k
フォーク
484
平均マージ
20時間 43分
マージ済み PR(30日)
263

環境構築

Codespaces で開く

このプロジェクトの開発コンテナを、あなたの GitHub アカウントでブラウザ上に起動します。

はじめの一歩

  1. issue を最後まで読み、次にプロジェクトのコントリビューションガイドを読みます。
  2. 着手することを issue にコメントします — 二人が同じ作業をするのを防げます。
  3. リポジトリをフォークし、ブランチを切って変更します。
  4. issue 番号を参照したプルリクエストを送ります。

rescript-lang/rescript のほかの issue

rescript-lang/rescript の issue をすべて見る

似ている issue

Compilers の issue をもっと見る

新しい issue をメールで受け取る

初心者向けの GitHub issue を短くまとめたダイジェスト。