Avoid using `()` in `derive(From)` output. #145550

nnethercote · 2025-08-18T04:53:53Z

Using an error type instead of () avoids the duplicated errors on struct SUnsizedField in deriving-from-wrong-target.rs. It also improves the expanded output from this:

struct S2(u32, u32);
impl ::core::convert::From<()> for S2 {
    #[inline]
    fn from(value: ()) -> S2 { (/*ERROR*/) }
}

to this:

struct S2(u32, u32);
impl ::core::convert::From<(/*ERROR*/)> for S2 {
    #[inline]
    fn from(value: (/*ERROR*/)) -> S2 { (/*ERROR*/) }
}

The new code also only matchs on item.kind once.

r? @Kobzol

Kobzol · 2025-08-18T05:15:02Z

Huh, I also tried ty::Err, but I could swear it just generated (). Maybe I held it wrong or didn't rebuild or something.

Thank you!

@bors r+ rollup

bors · 2025-08-18T05:15:05Z

📌 Commit dda17c5 has been approved by Kobzol

It is now in the queue for this repository.

…=Kobzol Avoid using `()` in `derive(From)` output. Using an error type instead of `()` avoids the duplicated errors on `struct SUnsizedField` in `deriving-from-wrong-target.rs`. It also improves the expanded output from this: ``` struct S2(u32, u32); impl ::core::convert::From<()> for S2 { #[inline] fn from(value: ()) -> S2 { (/*ERROR*/) } } ``` to this: ``` struct S2(u32, u32); impl ::core::convert::From<(/*ERROR*/)> for S2 { #[inline] fn from(value: (/*ERROR*/)) -> S2 { (/*ERROR*/) } } ``` The new code also only matchs on `item.kind` once. r? `@Kobzol`

Rollup of 19 pull requests Successful merges: - #140956 (`impl PartialEq<{str,String}> for {Path,PathBuf}`) - #141744 (Stabilize `ip_from`) - #144804 (Don't warn on never to any `as` casts as unreachable) - #144983 (Rehome 37 `tests/ui/issues/` tests to other subdirectories under `tests/ui/`) - #145025 (run spellcheck as a tidy extra check in ci) - #145041 (rework GAT borrowck limitation error) - #145243 (take attr style into account in diagnostics) - #145359 (Fix bug where `rustdoc-js` tester would not pick the right `search.js` file if there is more than one) - #145429 (Couple of codegen_fn_attrs improvements) - #145452 (Do not strip binaries in bootstrap everytime if they are unchanged) - #145486 (Fix `unicode_data.rs` mention message) - #145489 (library: Migrate from `cfg_if` to `cfg_select`) - #145493 (remove `should_render` in `PrintAttribute` derive) - #145500 (Port must_use to the new target checking) - #145505 (Simplify span caches) - #145511 (Rust build fails on OpenBSD after using file_lock feature) - #145516 (Weekly `cargo update`) - #145533 (Reorder `lto` options from most to least optimizing) - #145550 (Avoid using `()` in `derive(From)` output.) r? `@ghost` `@rustbot` modify labels: rollup

…=Kobzol Avoid using `()` in `derive(From)` output. Using an error type instead of `()` avoids the duplicated errors on `struct SUnsizedField` in `deriving-from-wrong-target.rs`. It also improves the expanded output from this: ``` struct S2(u32, u32); impl ::core::convert::From<()> for S2 { #[inline] fn from(value: ()) -> S2 { (/*ERROR*/) } } ``` to this: ``` struct S2(u32, u32); impl ::core::convert::From<(/*ERROR*/)> for S2 { #[inline] fn from(value: (/*ERROR*/)) -> S2 { (/*ERROR*/) } } ``` The new code also only matchs on `item.kind` once. r? ``@Kobzol``

…=Kobzol Avoid using `()` in `derive(From)` output. Using an error type instead of `()` avoids the duplicated errors on `struct SUnsizedField` in `deriving-from-wrong-target.rs`. It also improves the expanded output from this: ``` struct S2(u32, u32); impl ::core::convert::From<()> for S2 { #[inline] fn from(value: ()) -> S2 { (/*ERROR*/) } } ``` to this: ``` struct S2(u32, u32); impl ::core::convert::From<(/*ERROR*/)> for S2 { #[inline] fn from(value: (/*ERROR*/)) -> S2 { (/*ERROR*/) } } ``` The new code also only matchs on `item.kind` once. r? `@Kobzol`

…=Kobzol Avoid using `()` in `derive(From)` output. Using an error type instead of `()` avoids the duplicated errors on `struct SUnsizedField` in `deriving-from-wrong-target.rs`. It also improves the expanded output from this: ``` struct S2(u32, u32); impl ::core::convert::From<()> for S2 { #[inline] fn from(value: ()) -> S2 { (/*ERROR*/) } } ``` to this: ``` struct S2(u32, u32); impl ::core::convert::From<(/*ERROR*/)> for S2 { #[inline] fn from(value: (/*ERROR*/)) -> S2 { (/*ERROR*/) } } ``` The new code also only matchs on `item.kind` once. r? ``@Kobzol``

Rollup of 33 pull requests Successful merges: - #139345 (Extend `QueryStability` to handle `IntoIterator` implementations) - #140740 (Add `-Zindirect-branch-cs-prefix`) - #142079 (nll-relate: improve hr opaque types support) - #142938 (implement std::fs::set_permissions_nofollow on unix) - #144767 (Correct some grammar in integer documentation) - #144906 (Require approval from t-infra instead of t-release on tier bumps) - #144983 (Rehome 37 `tests/ui/issues/` tests to other subdirectories under `tests/ui/`) - #145025 (run spellcheck as a tidy extra check in ci) - #145166 (suggest using `pub(crate)` for E0364) - #145255 (dec2flt: Provide more valid inputs examples) - #145306 (Add tracing to various miscellaneous functions) - #145336 (Hide docs for `core::unicode`) - #145429 (Couple of codegen_fn_attrs improvements) - #145452 (Do not strip binaries in bootstrap everytime if they are unchanged) - #145464 (Stabilize `const_pathbuf_osstring_new` feature) - #145474 (Properly recover from parenthesized use-bounds (precise capturing lists) plus small cleanups) - #145486 (Fix `unicode_data.rs` mention message) - #145493 (remove `should_render` in `PrintAttribute` derive) - #145505 (Simplify span caches) - #145510 (Visit and print async_fut local for async drop.) - #145511 (Rust build fails on OpenBSD after using file_lock feature) - #145532 (resolve: debug for block module) - #145533 (Reorder `lto` options from most to least optimizing) - #145537 (Do not consider a `T: !Sized` candidate to satisfy a `T: !MetaSized` obligation.) - #145538 (bufreader::Buffer::backshift: don't move the uninit bytes) - #145542 (triagebot: Don't warn no-mentions on subtree updates) - #145549 (Update rust maintainers in openharmony.md) - #145550 (Avoid using `()` in `derive(From)` output.) - #145556 (Allow stability attributes on extern crates) - #145560 (Remove unused `PartialOrd`/`Ord` from bootstrap) - #145568 (ignore frontmatters in `TokenStream::new`) - #145571 (remove myself from some adhoc-groups and pings) - #145576 (Add change tracker entry for `--timings`) r? `@ghost` `@rustbot` modify labels: rollup

Zalathar · 2025-08-19T08:12:44Z

Bors hasn't noticed that this PR now has conflicts with #145589.

@bors r-

Using an error type instead of `()` avoids the duplicated errors on `struct SUnsizedField` in `deriving-from-wrong-target.rs`. It also improves the expanded output from this: ``` struct S2(u32, u32); impl ::core::convert::From<()> for S2 { #[inline] fn from(value: ()) -> S2 { (/*ERROR*/) } } ``` to this: ``` struct S2(u32, u32); impl ::core::convert::From<(/*ERROR*/)> for S2 { #[inline] fn from(value: (/*ERROR*/)) -> S2 { (/*ERROR*/) } } ``` The new code also only matchs on `item.kind` once.

rustbot · 2025-08-19T08:17:39Z

This PR was rebased onto a different master commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

Zalathar · 2025-08-19T08:18:17Z

Rebased and re-blessed.

@bors r=Kobzol

bors · 2025-08-19T08:18:19Z

📌 Commit ebfac4e has been approved by Kobzol

It is now in the queue for this repository.

…=Kobzol Avoid using `()` in `derive(From)` output. Using an error type instead of `()` avoids the duplicated errors on `struct SUnsizedField` in `deriving-from-wrong-target.rs`. It also improves the expanded output from this: ``` struct S2(u32, u32); impl ::core::convert::From<()> for S2 { #[inline] fn from(value: ()) -> S2 { (/*ERROR*/) } } ``` to this: ``` struct S2(u32, u32); impl ::core::convert::From<(/*ERROR*/)> for S2 { #[inline] fn from(value: (/*ERROR*/)) -> S2 { (/*ERROR*/) } } ``` The new code also only matchs on `item.kind` once. r? `@Kobzol`

Rollup of 10 pull requests Successful merges: - #145538 (bufreader::Buffer::backshift: don't move the uninit bytes) - #145542 (triagebot: Don't warn no-mentions on subtree updates) - #145549 (Update rust maintainers in openharmony.md) - #145550 (Avoid using `()` in `derive(From)` output.) - #145556 (Allow stability attributes on extern crates) - #145560 (Remove unused `PartialOrd`/`Ord` from bootstrap) - #145568 (ignore frontmatters in `TokenStream::new`) - #145571 (remove myself from some adhoc-groups and pings) - #145576 (Add change tracker entry for `--timings`) - #145578 (Add VEXos "linked files" support to `armv7a-vex-v5`) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of #145550 - nnethercote:derive_from-no-unit, r=Kobzol Avoid using `()` in `derive(From)` output. Using an error type instead of `()` avoids the duplicated errors on `struct SUnsizedField` in `deriving-from-wrong-target.rs`. It also improves the expanded output from this: ``` struct S2(u32, u32); impl ::core::convert::From<()> for S2 { #[inline] fn from(value: ()) -> S2 { (/*ERROR*/) } } ``` to this: ``` struct S2(u32, u32); impl ::core::convert::From<(/*ERROR*/)> for S2 { #[inline] fn from(value: (/*ERROR*/)) -> S2 { (/*ERROR*/) } } ``` The new code also only matchs on `item.kind` once. r? ``@Kobzol``

Rollup of 10 pull requests Successful merges: - rust-lang/rust#145538 (bufreader::Buffer::backshift: don't move the uninit bytes) - rust-lang/rust#145542 (triagebot: Don't warn no-mentions on subtree updates) - rust-lang/rust#145549 (Update rust maintainers in openharmony.md) - rust-lang/rust#145550 (Avoid using `()` in `derive(From)` output.) - rust-lang/rust#145556 (Allow stability attributes on extern crates) - rust-lang/rust#145560 (Remove unused `PartialOrd`/`Ord` from bootstrap) - rust-lang/rust#145568 (ignore frontmatters in `TokenStream::new`) - rust-lang/rust#145571 (remove myself from some adhoc-groups and pings) - rust-lang/rust#145576 (Add change tracker entry for `--timings`) - rust-lang/rust#145578 (Add VEXos "linked files" support to `armv7a-vex-v5`) r? `@ghost` `@rustbot` modify labels: rollup

rustbot assigned Kobzol Aug 18, 2025

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Aug 18, 2025

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Aug 18, 2025

Zalathar mentioned this pull request Aug 18, 2025

Rollup of 19 pull requests #145552

Closed

Zalathar mentioned this pull request Aug 18, 2025

Rollup of 18 pull requests #145566

Closed

jhpratt mentioned this pull request Aug 18, 2025

Rollup of 33 pull requests #145588

Closed

bors added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Aug 19, 2025

Zalathar force-pushed the derive_from-no-unit branch from dda17c5 to ebfac4e Compare August 19, 2025 08:17

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Aug 19, 2025

jieyouxu mentioned this pull request Aug 19, 2025

Rollup of 10 pull requests #145601

Merged

bors merged commit e462a7d into rust-lang:master Aug 20, 2025
10 checks passed

rustbot added this to the 1.91.0 milestone Aug 20, 2025

nnethercote deleted the derive_from-no-unit branch August 20, 2025 05:01

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Avoid using `()` in `derive(From)` output. #145550

Avoid using `()` in `derive(From)` output. #145550

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nnethercote commented Aug 18, 2025

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Avoid using () in derive(From) output. #145550

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Avoid using `()` in `derive(From)` output. #145550

Avoid using `()` in `derive(From)` output. #145550