Remove dead code from bun_css, bun_semver, and the re-export lists of 10 crates

[robobun]

Behaviour change: none

Problem

• Six trait impls in bun_css and bun_semver have no user on any target. A --gc-sections link of the debug objects discards all their methods, and no source line needs them.
• Ten crates re-export 24 names that no other crate imports. With pub rewritten to pub(crate), rustc reports each one as unused_imports.

Fix

• Delete the impls: DeepClone and CssEql for the arena ArrayList and for bun_ast::Loc, the helper eql_list, PartialCmp for CSSInteger, and Slicable for ExternalString.
• Trim the 24 names from the pub use lists. Four bun_ini structs lose their only outside path and become pub(crate). The non-unix FdT alias loses its only user and is deleted.
• Correct because nothing instantiates the removed impls, and the workspace compiles on every target triple with the deny lints on (what ran where is in Notes).
• No new test: no caller can observe a difference. Existing tests that cover this code: test/js/bun/css/css.test.ts, test/cli/install/semver.test.ts, test/js/bun/ini/ini.test.ts, test/cli/run/env.test.ts.

Background

• The workspace denies dead_code, but rustc exempts each pub item that a crate root can reach. A pub impl or re-export can stay after its last user is gone.
• DeepClone, CssEql, and PartialCmp are the CSS value protocol traits in src/css/generics.rs. Generated and hand-written CSS types call them through trait bounds.
• Slicable lets Lockfile::str read a semver string out of the lockfile string buffer. Only semver::String is passed to it.

Notes

Removed items:

• src/css/generics.rs: impl DeepClone for ArrayList<'bump, T>, impl DeepClone for bun_ast::Loc, fn eql_list, impl CssEql for ArrayList<'bump, T>, impl CssEql for bun_ast::Loc, impl PartialCmp for CSSInteger. rg -w eql_list src has no other hit.
• src/semver/lib.rs: impl Slicable for ExternalString.
• src/dotenv/lib.rs: re-export DirEntryProbe.
• src/ini/lib.rs: re-exports ConfigIterator, ScopeItem, ScopeIterator, ToStringFormatter. The four structs become pub(crate) because unreachable_pub is denied. All four are still used inside the crate.
• src/install/isolated_install/Store.rs: re-export StoreKeyFormatter.
• src/js_parser_jsc/lib.rs: re-export toml_datetime_to_js.
• src/paths/lib.rs: re-exports PlatformT, RelPathFacts, windows_volume_name_len, EnvPathInput, PathComponentBuilder.
• src/spawn_sys/lib.rs: re-exports FdT, IoCounters, WinRusage, WinTimeval.
• src/spawn_sys/spawn_process.rs: the alias #[cfg(not(unix))] pub type FdT = i32;. Every use of FdT is in #[cfg(unix)] code, so the re-export was the only thing that named the non-unix alias. The mordant job found this (unused_pub, 1 finding over a baseline of 0). The comment on the bun_windows_sys dependency in src/spawn_sys/Cargo.toml named the removed re-export, so it now names the alias in spawn_process.rs.
• src/tcc_sys/lib.rs: re-exports ErrorFunc, TCCErrorFunc, TCCState.
• src/threading/lib.rs: re-export GuardedLock.
• src/uws_sys/lib.rs: re-export PosixLoop.
• src/watcher/lib.rs: re-exports MAX_EVICTION_COUNT, WatchItem, WatchItemIndex.

For each re-exported name, rg -w <name> finds it in no other crate, in no generated Rust under the codegen directory, and in no path of the form crate::<name> or <crate>::<name>. Except for the non-unix FdT alias, the items themselves stay, because each one is still used inside its own crate.

How the candidates were found:

1. The debug objects were linked again with --gc-sections --print-gc-sections. 615 Rust functions, methods, and trait impls outside the files of the open dead-code PRs have no surviving symbol.
2. All 615 were deleted at once. cargo check ran in a loop for linux-gnu, linux-gnu --tests, windows-msvc, apple-darwin, freebsd, android, and musl. Each item that an error named was restored. 12 items survived. Most of the others are Windows-only or macOS-only code.
3. Each crate was checked once with pub rewritten to pub(crate). This shows the re-exports and items that are unused inside their own crate. Names that appear in any other crate were kept.

Candidates that compiled without them but are not dead, and so are not in this PR:

• ArrayBufferSink::flush, FetchRequestBodySink::flush, BorderImageSideWidth::deep_clone. A macro-generated trait method forwards to each inherent method (Self::flush(self), <$t>::deep_clone(self, bump)). Without the inherent method the trait method calls itself. The unconditional_recursion lint catches it.
• bun_zstd::inflate_embedded and inflate_embedded_nul. embed_compressed! calls them only under cfg(bun_codegen_embed), which only release builds set.

A removed impl is not always a compile error. A call like a.eql(&b) on two ArrayList values falls back to impl CssEql for [T] through auto-deref. That impl compares the length and then each element, the same as the removed eql_list. On the base of the first commit, no symbol of a removed impl survived the link, so no reachable code called one.

Overlap with other open dead-code PRs: #43976 also edits src/uws_sys/lib.rs, in other hunks. No other file in this PR is touched by one.

What ran on which tree:

• First commit (base 2dee3bd): bun bd, bun run rust:check-all (12 of 12), and these test files with the debug build: test/js/bun/css/css.test.ts, test/cli/install/semver.test.ts, test/js/bun/ini/ini.test.ts, test/cli/run/env.test.ts, test/internal/source-lints/ (174 tests), test/js/bun/resolve/toml/toml.test.js, test/js/node/path/resolve.test.js, test/js/bun/ffi/cc.test.ts, test/cli/install/bun-lock.test.ts.
• After the merge of main (f063852) plus the FdT commit: cargo check --workspace for the host, and bun run rust:check-all for both Windows triples (2 of 2). The FdT commit changes only code that is compiled out on unix, and CI built the merge commit on every platform (build 120695). The debug build and the test files were not run again locally.

---

[policy-decision:dep] gate passed · iteration 6 · 14 files touched

passes on PR (with fix)

Dependency/toolchain change; no test proof to run.

diff hotspot

src/css/generics.rs                   | 52 -----------------------------------
 src/dotenv/lib.rs                     |  4 +--
 src/ini/lib.rs                        | 13 ++++-----
 src/install/isolated_install/Store.rs |  2 +-
 src/js_parser_jsc/lib.rs              |  3 +-
 src/paths/lib.rs                      |  7 ++---
 src/semver/lib.rs                     |  6 ----
 src/spawn_sys/Cargo.toml              |  2 +-
 src/spawn_sys/lib.rs                  |  4 +--
 src/spawn_sys/spawn_process.rs        |  2 --
 src/tcc_sys/lib.rs                    |  4 +--
 src/threading/lib.rs                  |  2 +-
 src/uws_sys/lib.rs                    |  2 +-
 src/watcher/lib.rs                    |  6 ++--
 14 files changed, 21 insertions(+), 88 deletions(-)

gate history · 1 passed · 3 rejected · iteration 6

evidence per changed file

file                                   reads  edits  tests
src/css/generics.rs                        0      0      1
src/dotenv/lib.rs                          0      0      1
src/ini/lib.rs                             0      0      1
src/install/isolated_install/Store.rs      0      0      1
src/js_parser_jsc/lib.rs                   0      0      1
src/paths/lib.rs                           0      0      1
src/semver/lib.rs                          0      0      1
src/spawn_sys/Cargo.toml                   1      2      0
src/spawn_sys/lib.rs                       0      0      2
src/spawn_sys/spawn_process.rs             1      1      2
src/tcc_sys/lib.rs                         0      0      1
src/threading/lib.rs                       0      0      1
src/uws_sys/lib.rs                         0      0      2
src/watcher/lib.rs                         0      0      1

[robobun]

Status: ready for review.

• Head ae7797c is the merge of main plus one commit. That commit deletes the non-unix FdT alias, which the mordant job flagged after the FdT re-export was removed.
• Scope: 14 files, 88 lines removed, 21 added. No behaviour changes: the diff only deletes unused trait impls, unused re-exports, and one unused type alias.
• Checked locally on this head: cargo check --workspace for the host and for both Windows triples, with the deny lints on. The first commit was also checked on all 12 target triples and with the debug build and the test files named in the PR body.
• CI built the merge commit 39b8b5e on every platform (build #120695). No job of that build had failed when ae7797c was pushed.
• Remove dead code from the bake client, uSockets, uWS HTTP/2, uws_sys, and the CI pipeline script #43976 also edits src/uws_sys/lib.rs, in other hunks. No other file here is touched by an open dead-code PR.

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📒 Files selected for processing (2)

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• src/spawn_sys/spawn_process.rs

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---

Walkthrough

The pull request narrows public API surfaces across multiple crates. It removes selected CSS trait implementations, restricts four INI types to crate visibility, and removes selected crate-root re-exports. It also removes a non-Unix FdT alias and rewords a dependency comment.

Changes

API surface cleanup

Layer / File(s)	Summary
CSS trait implementation cleanup src/css/generics.rs	Removes selected DeepClone, CssEql, and PartialCmp implementations and the private eql_list helper.
INI visibility reduction src/ini/lib.rs	Removes four public re-exports and changes the corresponding types to pub(crate).
Crate-root re-export reduction src/dotenv/lib.rs, src/install/isolated_install/Store.rs, src/js_parser_jsc/lib.rs, src/paths/lib.rs, src/semver/lib.rs, src/spawn_sys/*, src/tcc_sys/lib.rs, src/threading/lib.rs, src/uws_sys/lib.rs, src/watcher/lib.rs	Removes selected public re-exports. In spawn_sys, the non-Unix FdT alias is removed, and a dependency comment is reworded.

Priority: ⬇️ Low

Merge Risk: ⚪ Minimal · up to ae779

The changes narrow Rust API surfaces as intended, with no production behavior change apparent. No concrete merge-blocking risk is established.

🚥 Pre-merge checks | ✅ 4

✅ 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	The description clearly explains what the PR changes and provides detailed verification notes, including checks, tests, target triples, and known limitations.
Title check	✅ Passed	The title is concise, specific, and accurately summarizes the dead-code removal and re-export cleanup.

---

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

[claude]

Code review found no issues

No high-confidence issues detected in this change.

6 verified lower-impact observations (convention, logging or cleanup points) were not posted.

[robobun]

^{Updated 2:03 PM PT - Sep 25th, 2026}

✅ @robobun, your commit ae7797c39cb9dff564724852428e34f8c9bfe95d passed in Build #120698! 🎉

---

🧪   To try this PR locally:

bunx bun-pr 43010

That installs a local version of the PR into your bun-43010 executable, so you can run:

bun-43010 --bun

[robobun]

@alii Head 39b8b5e made the mordant job fail, and the cause was this diff. Commit ae7797c fixes it. Please merge only a head that includes ae7797c.

• With the FdT re-export gone from src/spawn_sys/lib.rs, the #[cfg(not(unix))] pub type FdT = i32; alias in src/spawn_sys/spawn_process.rs had no user. Every use of FdT is in #[cfg(unix)] code.
• mordant-baseline.toml allows 0 unused_pub findings in that file, so the job reported 1 finding over the baseline.
• ae7797c deletes the alias. Checked locally before the push: cargo check --workspace for the host and for both Windows triples, with the deny lints on. The alias is compiled only on non-unix targets.

The push restarted CI.

[claude]

LGTM — mechanical dead-code sweep; the new FdT commit checks out too.

What was reviewed:

• The removed #[cfg(not(unix))] FdT alias: every remaining FdT use in src/spawn_sys/spawn_process.rs is inside the #[cfg(unix)] spawn function (line 632 onward) or the linux/android-gated PidFdType, so nothing names it on Windows.
• Each trimmed re-export, grepped across all .rs files including cfg-gated code: out-of-crate hits are doc comments only; in-crate uses go through crate::/still-pub module paths (bun_threading::guarded, bun_paths::resolve_path).
• The bun_ini structs narrowed to pub(crate) are only constructed inline in-crate and appear in no pub signature; the removed Slicable for ExternalString has no caller passing an ExternalString to Lockfile::str/str_detached.

Extended reasoning...

The diff (+21/-88 across 14 Rust files) deletes six unused trait impls in bun_css/bun_semver, trims 24 names from crate-root pub use lists in ten crates, narrows four bun_ini structs to pub(crate), drops the non-unix FdT alias, and rewords one Cargo.toml comment; it touches no security-sensitive surface and no behavior. Since the prior review, the only substantive change is the FdT alias removal plus a merge of main, and I verified by reading the cfg gates that the alias has no non-unix consumer. No changed path is covered by CODEOWNERS, the hunt ran dry, and grep of the whole tree (including #[cfg(windows)] code) found no consumer of any removed name, which decided approve; the one limitation is that cargo could not be run in this sandbox, so the cross-target check rests on grep plus the author's reported rust:check-all runs.