Do not suppress the fn item uniqueness note for late bound lifetimes by zakrad · Pull Request #161894 · rust-lang/rust

zakrad · 2026-08-27T22:24:40Z

Fixes #145558 same_type_modulo_infer compared the bound regions by identity, so the note was suppressed for late bound lifetimes and anonymizing the binders fixes it.

I authored and reviewed the change and used LLM to help locate the code and validate the fix

rustbot · 2026-08-27T22:24:45Z

r? @nnethercote

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nnethercote

Suggestion for next time: when doing error message improvements it's nice to add the new test in a first commit, and then make the error message change in the second commit. That way it's easy for the reviewer to see exactly how the error message changed.

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nnethercote · 2026-08-30T22:16:49Z

                    || !found_sig.is_suggestable(self.tcx, true)
                    || !expected_sig.is_suggestable(self.tcx, true)
                    || self.tcx.intrinsic(*did1).is_some()
                    || self.tcx.intrinsic(*did2).is_some()


Should this condition be updated to use expected_sig_anon and found_sign_anon?

I tried, it makes the as fn(..) help trigger and then prints as fn(&'^0.Named(DefId(0:6 ~ lt[99a7]::f1::'a)) A) which looks like a separate pre existing issue with that help, so I left it as is.

nnethercote · 2026-08-30T22:24:16Z

This seems reasonable to me, modulo the mentioned nit. But anything involving for<'a> is out of my comfort zone and an expert should probably take a look, so...

r? types

zakrad · 2026-08-31T10:11:50Z

Splitted as suggested @rustbot ready

zakrad · 2026-09-14T07:18:35Z

ping @jackh726

jackh726 · 2026-09-19T20:06:14Z

@bors r+

rust-bors · 2026-09-19T20:06:17Z

📌 Commit 21228c2 has been approved by jackh726

It is now in the queue for this repository.

…-145558, r=jackh726 Do not suppress the fn item uniqueness note for late bound lifetimes Fixes rust-lang#145558 `same_type_modulo_infer` compared the bound regions by identity, so the note was suppressed for late bound lifetimes and anonymizing the binders fixes it.

Rollup of 13 pull requests Successful merges: - #158515 (Make let-else respect macro_rules expr metavariable grouping) - #160097 (fix const_item_mutation lint to use needs_drop instead of has_dtor) - #161435 (Provide a `supertrait_def_ids()` function in rustc_type_ir's interner) - #161894 (Do not suppress the fn item uniqueness note for late bound lifetimes) - #162990 (post GH comment on types nominations) - #154665 (add safety section for mem::zeroed) - #162700 ( Remove incorrect parse error recovery code that mistakes `as` casts for the long removed type ascription) - #162705 (Trigger "C array" parse error recovery in far fewer cases) - #162875 (Add .seek_read_exact(), .seek_write_all() to std::os::windows::fs::FileExt) - #162988 (recover `true` and `false` in type position as `bool`) - #162995 (Constify `impl FromStr for NonZero<T>`) - #163006 (Use `end_point` for trailing brace in `let...else` diagnostics) - #163007 (add Dir::try_clone)

…-145558, r=jackh726 Do not suppress the fn item uniqueness note for late bound lifetimes Fixes rust-lang#145558 `same_type_modulo_infer` compared the bound regions by identity, so the note was suppressed for late bound lifetimes and anonymizing the binders fixes it.

…uwer Rollup of 15 pull requests Successful merges: - #158515 (Make let-else respect macro_rules expr metavariable grouping) - #162726 (std: fix unix socket address panic on a full sun_path) - #160028 (Better account for `Self` that might be a typo of `self`) - #160097 (fix const_item_mutation lint to use needs_drop instead of has_dtor) - #161435 (Provide a `supertrait_def_ids()` function in rustc_type_ir's interner) - #161894 (Do not suppress the fn item uniqueness note for late bound lifetimes) - #162990 (post GH comment on types nominations) - #154665 (add safety section for mem::zeroed) - #162700 ( Remove incorrect parse error recovery code that mistakes `as` casts for the long removed type ascription) - #162705 (Trigger "C array" parse error recovery in far fewer cases) - #162875 (Add .seek_read_exact(), .seek_write_all() to std::os::windows::fs::FileExt) - #162988 (recover `true` and `false` in type position as `bool`) - #162995 (Constify `impl FromStr for NonZero<T>`) - #163006 (Use `end_point` for trailing brace in `let...else` diagnostics) - #163007 (add Dir::try_clone)

Rollup of 17 pull requests Successful merges: - #158515 (Make let-else respect macro_rules expr metavariable grouping) - #160028 (Better account for `Self` that might be a typo of `self`) - #160097 (fix const_item_mutation lint to use needs_drop instead of has_dtor) - #161435 (Provide a `supertrait_def_ids()` function in rustc_type_ir's interner) - #161894 (Do not suppress the fn item uniqueness note for late bound lifetimes) - #162990 (post GH comment on types nominations) - #153662 (Suggest fully qualified path on method name collision) - #154665 (add safety section for mem::zeroed) - #159787 (Prefer ModId in more places) - #162700 ( Remove incorrect parse error recovery code that mistakes `as` casts for the long removed type ascription) - #162705 (Trigger "C array" parse error recovery in far fewer cases) - #162875 (Add .seek_read_exact(), .seek_write_all() to std::os::windows::fs::FileExt) - #162988 (recover `true` and `false` in type position as `bool`) - #162995 (Constify `impl FromStr for NonZero<T>`) - #163006 (Use `end_point` for trailing brace in `let...else` diagnostics) - #163007 (add Dir::try_clone) - #163039 (Use verbose suggestion for parenthetical `Fn` notation and fully-qualified path on ambiguous assoc item)

Rollup merge of #161894 - zakrad:fix-fn-item-note-late-bound-145558, r=jackh726 Do not suppress the fn item uniqueness note for late bound lifetimes Fixes #145558 `same_type_modulo_infer` compared the bound regions by identity, so the note was suppressed for late bound lifetimes and anonymizing the binders fixes it.

rustbot assigned nnethercote Aug 27, 2026

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 27, 2026

nnethercote reviewed Aug 30, 2026

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rustbot added the T-types Relevant to the types team, which will review and decide on the PR/issue. label Aug 30, 2026

rustbot assigned jackh726 and unassigned nnethercote Aug 30, 2026

nnethercote 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-review Status: Awaiting review from the assignee but also interested parties. labels Aug 30, 2026

zakrad added 2 commits August 31, 2026 13:21

Add test for the fn item uniqueness note with late bound lifetimes

98a157a

Do not suppress the fn item uniqueness note for late bound lifetimes

21228c2

zakrad force-pushed the fix-fn-item-note-late-bound-145558 branch from e378b8a to 21228c2 Compare August 31, 2026 09:57

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Aug 31, 2026

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 Sep 19, 2026

jhpratt mentioned this pull request Sep 19, 2026

Rollup of 13 pull requests #163035

Closed

JonathanBrouwer mentioned this pull request Sep 19, 2026

Rollup of 15 pull requests #163038

Closed

mu001999 mentioned this pull request Sep 20, 2026

Rollup of 17 pull requests #163043

Merged

rust-bors Bot merged commit a4e0bbb into rust-lang:main Sep 20, 2026
13 checks passed

rustbot added this to the 1.100.0 milestone Sep 20, 2026

zakrad deleted the fix-fn-item-note-late-bound-145558 branch September 20, 2026 15:13

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Do not suppress the fn item uniqueness note for late bound lifetimes - #161894

Do not suppress the fn item uniqueness note for late bound lifetimes#161894
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