Do not suggest `derive` if there is already an impl by WhyNovaa · Pull Request #150720 · rust-lang/rust

WhyNovaa · 2026-01-06T08:47:16Z

This PR fixes an issue where the compiler would suggest adding #[derive(Trait)] even if the struct or enum already implements that trait manually.

Fixes #146515

rustbot · 2026-01-06T08:47:22Z

r? @jieyouxu

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WhyNovaa · 2026-01-06T09:34:13Z

r? @BoxyUwU

rustbot · 2026-01-06T09:34:18Z

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compiler/rustc_hir_typeck/src/method/suggest.rs

lcnr · 2026-01-14T14:44:33Z

r? @lcnr

will get to it later this week/start of next

fmease · 2026-01-18T09:27:40Z

CC'ing brand new PR #151278 for visibility. It attempts to address a related issue. We might or might not be able to share the "core logic" between these two diagnostics (disclaimer: I've only skimmed both PRs, so I might be entirely wrong).

compiler/rustc_hir_typeck/src/method/suggest.rs

lcnr

nits, then r=me

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rustbot · 2026-01-28T09:09:24Z

This PR was rebased onto a different main 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.

lcnr · 2026-01-28T09:47:27Z

@bors r+

rust-bors · 2026-01-28T09:47:30Z

📌 Commit 11ae531 has been approved by lcnr

It is now in the queue for this repository.

…uwer Rollup of 12 pull requests Successful merges: - #150491 (resolve: Mark items under exported ambiguous imports as exported) - #150720 (Do not suggest `derive` if there is already an impl) - #150968 (compiler-builtins: Remove the no-f16-f128 feature) - #151493 ([RFC] rustc_parse: improve the error diagnostic for "missing let in let chain") - #151660 (Bump `std`'s `backtrace`'s `rustc-demangle`) - #151696 (Borrowck: Simplify SCC annotation computation, placeholder rewriting) - #151704 (Implement `set_output_kind` for Emscripten linker) - #151706 (Remove Fuchsia from target OS list in unix.rs for sleep) - #151769 (fix undefined behavior in VecDeque::splice) - #151779 (stdarch subtree update) - #151449 ([rustdoc] Add regression test for #151411) - #151773 (clean up checks for constant promotion of integer division/remainder operations)

…uwer Rollup of 12 pull requests Successful merges: - rust-lang/rust#150491 (resolve: Mark items under exported ambiguous imports as exported) - rust-lang/rust#150720 (Do not suggest `derive` if there is already an impl) - rust-lang/rust#150968 (compiler-builtins: Remove the no-f16-f128 feature) - rust-lang/rust#151493 ([RFC] rustc_parse: improve the error diagnostic for "missing let in let chain") - rust-lang/rust#151660 (Bump `std`'s `backtrace`'s `rustc-demangle`) - rust-lang/rust#151696 (Borrowck: Simplify SCC annotation computation, placeholder rewriting) - rust-lang/rust#151704 (Implement `set_output_kind` for Emscripten linker) - rust-lang/rust#151706 (Remove Fuchsia from target OS list in unix.rs for sleep) - rust-lang/rust#151769 (fix undefined behavior in VecDeque::splice) - rust-lang/rust#151779 (stdarch subtree update) - rust-lang/rust#151449 ([rustdoc] Add regression test for rust-lang/rust#151411) - rust-lang/rust#151773 (clean up checks for constant promotion of integer division/remainder operations)

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 Jan 6, 2026

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rustbot added has-merge-commits PR has merge commits, merge with caution. S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jan 6, 2026

WhyNovaa force-pushed the diagnostics-impl-fix branch from e01da01 to 197a3ea Compare January 6, 2026 09:02

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WhyNovaa force-pushed the diagnostics-impl-fix branch from 197a3ea to 91788da Compare January 6, 2026 09:11

rustbot assigned BoxyUwU and unassigned jieyouxu Jan 6, 2026

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rustbot assigned lcnr and unassigned Kivooeo Jan 14, 2026

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WhyNovaa force-pushed the diagnostics-impl-fix branch from 40a83bf to ed85443 Compare January 14, 2026 15:05

fmease mentioned this pull request Jan 18, 2026

Provide more context on trait bounds being unmet due to imperfect derive #151278

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lcnr changed the title ~~Diagnostics impl fix~~ Do not suggest derive if there is already an impl Jan 27, 2026

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WhyNovaa force-pushed the diagnostics-impl-fix branch from ba92274 to bd3503d Compare January 28, 2026 09:07

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WhyNovaa force-pushed the diagnostics-impl-fix branch from daeb392 to 7a4b3ed Compare January 28, 2026 09:33

rustbot removed has-merge-commits PR has merge commits, merge with caution. S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jan 28, 2026

diagnostics: don't suggest #[derive] if impl already exists

11ae531

WhyNovaa force-pushed the diagnostics-impl-fix branch from 7a4b3ed to 11ae531 Compare January 28, 2026 09:39

rust-bors bot 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 Jan 28, 2026

JonathanBrouwer mentioned this pull request Jan 28, 2026

Rollup of 12 pull requests #151794

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rust-bors bot merged commit 3787595 into rust-lang:main Jan 29, 2026
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rustbot added this to the 1.95.0 milestone Jan 29, 2026

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WhyNovaa commented Jan 6, 2026 •

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