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Formatter drops comments in dict patterns, variant spread patterns and dict literal spreads

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已经有一个关联 PR 被合并了。

  • #8850 来自 @cknitt —— 已合并

评估

难度
3/5
预计耗时
1-2 天
新手友好度
35/100
Issue 类型
缺陷
描述清晰度
描述清楚
活跃度
停滞
技术栈
ocaml
领域
testing, tooling

调研方向

Start with res_comments_table.ml and res_printer.ml at the locations linked in the issue, then review the comment fixtures under tests/syntax_tests/data/printer/comments/. Reproduce with the provided cm.res command and add fixture cases for dict patterns and variant spread patterns. Done means formatting preserves every listed comment and the fixtures catch losses on the first print.

由索引模型根据 Issue 内容生成。

描述

Found by adversarial experiments on semantic analysts.

What is broken

The formatter deletes comments in these positions:

  • Dict pattern key: | dict{"a" /* k */: b} → | dict{"a": b}
  • Dict pattern value: | dict{"a": /* c */ a} → | dict{"a": a} (the record pattern {a: /* c */ a} keeps its comment)
  • Empty dict pattern: | dict{/* e */} → | dict{}
  • Variant spread pattern: | .../* c */ t → | ...t
  • Polymorphic variant type pattern: | #.../* c */ t → | #...t
  • Dict literal with a spread: an own-line comment before the first row after a spread is dropped (/* x */ on the same line is kept)

Reproduction

cm.res:

let f = d =>
  switch d {
  | dict{"a" /* k */: b} => b
  | dict{"a": /* c */ a} => a
  | dict{/* e */} => 0
  | _ => 1
  }
type t = A | B
type u = | ...t | C
let g = x =>
  switch x {
  | .../* c */ t => 0
  | #.../* c */ t => 0
  | C => 1
  }
let b = dict{
  ...base,
  // first
  "a": 1,
}

./_build/default/compiler/syntax/cli/res_cli.exe cm.res

Observed: every comment above is missing from the output. Expected: each comment is printed.

Where

No comment fixture covers dict patterns or variant spread patterns (tests/syntax_tests/data/printer/comments/). The roundtrip test compares the first formatting with the second, so a comment lost on the first print passes. The fix should add these cases to the comment fixtures.

Introduced by

The same output is produced at ece8b148, before the dict pattern and variant spread nodes existed. The current code comes from b081cd19c (#8749) and bffd18e7b (#8742).

Impact

Running the formatter silently deletes user comments.

主要语言
OCaml
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