Diagnostics: inline-record mutability coercion gives no reason, and `throw` in `finally` warns about unreachable code

未关闭
  • 哪里不对？
#9,185 0 条评论 0 个 reaction 已指派 0 人 在 GitHub 查看

维护者通常 1 天内回复

还没有人认领这个 Issue。

评估

难度
4/5
预计耗时
3-5 天
新手友好度
38/100
Issue 类型
缺陷
描述清晰度
基本清楚
活跃度
活跃
技术栈
ocaml
领域
compilers, developer-experience

调研方向

The throw-in-finally case points to compiler/ml/typecore.ml around lines 2920-2922, where the finally block is typed as a statement; check how warning 21 is raised for non-returning statements. The inline-record coercion error is reached through a subtype path the payload does not name, so locate it by searching for the existing plain-record mutability explanation and compare the two. Run the two snippets from the issue to confirm the wrong output, and count done as the mutable-field explanation appearing for inline records and warning 21 no longer firing for throw in finally.

由索引模型根据 Issue 内容生成。

描述

Found by differential semantic drift analysis from b123b7c3 to c10223e8.

What is broken

  • Coercion into an inline record with a mutable field gives no reason (#9086). The coercion is now rejected, correctly:

    type v1 = A({x: float})
type v2 = A({mutable x: float})
let a: v1 = A({x: 0.})
let b = (a :> v2)

    The error is only Type v1 is not a subtype of v2. For a field of a plain record type ({r: r1} into {r: r2}) the error explains: "The field x is mutable in record r2, but not in record r1. A coercion can't make a field writable."

  • throw in finally gives warning 21 (#8931):

    exception B
let k = () => try { 1 } finally { throw(B) }

    Warning 21: "This statement does not continue execution; following code is unreachable." No code follows the throw; the generated JavaScript is correct. The finally block is typed as a statement (typecore.ml L2920-L2922), and a non-returning statement triggers this warning.

Possible cause (speculation only)

The inline-record path reports the subtype failure before reaching the field comparison that produces the explanation for plain records.

🤖 Generated with Claude Code

主要语言
OCaml
星标
7.5k
派生
484
平均合并
16 小时 57 分钟
30 天内合并 PR
258

环境准备

在 Codespaces 中打开

在浏览器里用你自己的 GitHub 账号启动这个项目的开发容器。

从这里开始

  1. 先读完整个 Issue，再读项目的贡献指南。
  2. 在 Issue 下留言说明你要接手 —— 这能避免两个人做同样的事。
  3. Fork 仓库，在一个分支上完成修改。
  4. 提交 Pull Request，并在描述里引用这个 Issue 编号。

rescript-lang/rescript 的其他 Issue

查看 rescript-lang/rescript 的全部 Issue

相似的 Issue

更多 Compilers Issue

把新 issue 发到你的邮箱

精选适合新手参与的 GitHub issue 摘要。