fix refining_impl_trait suggestion with return_type_notation by enthropy7 · Pull Request #151744 · rust-lang/rust

enthropy7 · 2026-01-27T14:50:27Z

using #![feature(return_type_notation)] on top of refining_impl_trait made the lint suggest a pretty wild “wrap the body in <Self as Trait>::f(..)” fix instead of the simple “just copy the return type from the trait”. this patch makes the lint always suggest the plain return-type replacement based on the trait signature (by grabbing the original snippet when possible), so you don’t get RTN-style desugarings in the help

new test here

fixes #151663

rustbot · 2026-01-27T14:50:35Z

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fmease · 2026-01-27T15:47:18Z

compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs

@@ -332,6 +332,16 @@ fn report_mismatched_rpitit_signature<'tcx>(
            hir::FnRetTy::Return(ty) => ty.span,
        });



I'm interested in the reason why the type gets printed that way under RTN. I would look in the HIR pretty printer to look for the culprit. Once identified, there might be a more robust solution because using span_to_snippet is more like hot patching the bug (e.g., if the source is not available (so None) I'm pretty sure we will continue to print the type that way under RTN).

pretty_print_rpitit used RtnMode::ForDiagnostic by default. it gives impl Trait { T::method(..) } while RTN.

davidtwco · 2026-02-05T16:21:52Z

@bors r+ rollup

rust-bors · 2026-02-05T16:21:56Z

📌 Commit 849725e has been approved by davidtwco

It is now in the queue for this repository.

…rtn, r=davidtwco fix refining_impl_trait suggestion with return_type_notation using `#![feature(return_type_notation)] `on top of `refining_impl_trait` made the lint suggest a pretty wild “wrap the body in `<Self as Trait>::f(..)”` fix instead of the simple “just copy the return type from the trait”. this patch makes the lint always suggest the plain return-type replacement based on the trait signature (by grabbing the original snippet when possible), so you don’t get RTN-style desugarings in the help new test here fixes rust-lang#151663

…uwer Rollup of 9 pull requests Successful merges: - #151278 (Provide more context on trait bounds being unmet due to imperfect derive) - #151955 (escape symbol names in global asm) - #149329 (Mark match arms in try and for as being from desugarings.) - #151474 (Minor structural improvements) - #151744 (fix refining_impl_trait suggestion with return_type_notation) - #152107 (Convert to inline diagnostics in `rustc_borrowck`) - #152117 (Convert to inline diagnostics in `rustc_trait_selection`) - #152136 (Consolidate type const checks on `tcx.is_type_const`) - #152170 (Port `rustc_effective_visibility` to the new attribute parser)

…rtn, r=davidtwco fix refining_impl_trait suggestion with return_type_notation using `#![feature(return_type_notation)] `on top of `refining_impl_trait` made the lint suggest a pretty wild “wrap the body in `<Self as Trait>::f(..)”` fix instead of the simple “just copy the return type from the trait”. this patch makes the lint always suggest the plain return-type replacement based on the trait signature (by grabbing the original snippet when possible), so you don’t get RTN-style desugarings in the help new test here fixes rust-lang#151663

…uwer Rollup of 11 pull requests Successful merges: - #152174 (stdarch subtree update) - #151278 (Provide more context on trait bounds being unmet due to imperfect derive) - #151955 (escape symbol names in global asm) - #149329 (Mark match arms in try and for as being from desugarings.) - #151474 (Minor structural improvements) - #151744 (fix refining_impl_trait suggestion with return_type_notation) - #152107 (Convert to inline diagnostics in `rustc_borrowck`) - #152117 (Convert to inline diagnostics in `rustc_trait_selection`) - #152136 (Consolidate type const checks on `tcx.is_type_const`) - #152170 (Port `rustc_effective_visibility` to the new attribute parser) - #152184 (Port rustc_abi to the attribute parser)

…rtn, r=davidtwco fix refining_impl_trait suggestion with return_type_notation using `#![feature(return_type_notation)] `on top of `refining_impl_trait` made the lint suggest a pretty wild “wrap the body in `<Self as Trait>::f(..)”` fix instead of the simple “just copy the return type from the trait”. this patch makes the lint always suggest the plain return-type replacement based on the trait signature (by grabbing the original snippet when possible), so you don’t get RTN-style desugarings in the help new test here fixes rust-lang#151663

…uwer Rollup of 13 pull requests Successful merges: - #152191 (Convert to inline diagnostics in `rustc_hir_analysis`) - #149329 (Mark match arms in try and for as being from desugarings.) - #151474 (Minor structural improvements) - #152107 (Convert to inline diagnostics in `rustc_borrowck`) - #152117 (Convert to inline diagnostics in `rustc_trait_selection`) - #152136 (Consolidate type const checks on `tcx.is_type_const`) - #152140 (Hard code the error code registry for custom drivers) - #152155 (Fix typos in riscv64a23-unknown-linux-gnu.md) - #152170 (Port `rustc_effective_visibility` to the new attribute parser) - #152182 (update compiler stable backport zulip msg) - #152184 (Port rustc_abi to the attribute parser) - #152195 (update openmp/offload builds to LLVM 22, Part 1) - #152202 (chore: clearify tidy's error message) Failed merges: - #151744 (fix refining_impl_trait suggestion with return_type_notation) - #152212 (Port some attributes to the attr parser)

rustbot · 2026-02-06T13:22:56Z

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.

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 27, 2026

rustbot assigned davidtwco Jan 27, 2026

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enthropy7 force-pushed the fix-refining-impl-trait-rtn branch from fb2bd79 to 34c9ebf Compare January 27, 2026 15:42

fmease reviewed Jan 27, 2026

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enthropy7 force-pushed the fix-refining-impl-trait-rtn branch from 34c9ebf to a7458f5 Compare January 27, 2026 19:09

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enthropy7 force-pushed the fix-refining-impl-trait-rtn branch 2 times, most recently from c81c4d4 to 8c9c35e Compare January 27, 2026 19:51

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enthropy7 force-pushed the fix-refining-impl-trait-rtn branch 2 times, most recently from e9229ca to 849725e Compare January 27, 2026 21:55

davidtwco approved these changes Feb 5, 2026

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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 Feb 5, 2026

JonathanBrouwer mentioned this pull request Feb 5, 2026

Rollup of 9 pull requests #152181

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Rollup of 11 pull requests #152185

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Rollup of 12 pull requests #152207

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Rollup of 12 pull requests #152208

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fix refining_impl_trait suggestion with return_type_notation

bcde3fc

enthropy7 force-pushed the fix-refining-impl-trait-rtn branch from 849725e to bcde3fc Compare February 6, 2026 13:22

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fix refining_impl_trait suggestion with return_type_notation#151744

fix refining_impl_trait suggestion with return_type_notation#151744
enthropy7 wants to merge 1 commit intorust-lang:mainfrom
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		@@ -332,6 +332,16 @@ fn report_mismatched_rpitit_signature<'tcx>(
		hir::FnRetTy::Return(ty) => ty.span,
		});

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enthropy7 commented Jan 27, 2026 •

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