suggest calling a fn item used as the iterator of a `for` loop by Albab-Hasan · Pull Request #161579 · rust-lang/rust

Albab-Hasan · 2026-08-23T08:37:01Z

suggest_fn_call only fired when the failing obligation came from ObligationCauseCode::FunctionArg, so a fn item or closure used as the iterator of a for loop got no structured suggestion to call it.

the iterator of a for loop is passed to IntoIterator::into_iter, so the failing Iterator goal is a derived obligation and the cause span carries the loop desugaring, which makes can_be_used_for_suggestions return false. carry the HirId of the iterator expression in ObligationCauseCode::ForLoopIterator and gate the suggestion on the span of that expression instead.

fixes #161564

r? @oli-obk

rustbot · 2026-08-23T08:37:06Z

oli-obk is not on the review rotation at the moment.
They may take a while to respond.

`suggest_fn_call` only fired when the failing obligation came from `ObligationCauseCode::FunctionArg`, so a fn item or closure used as the iterator of a `for` loop got no structured suggestion to call it. the iterator of a `for` loop is passed to `IntoIterator::into_iter`, so the failing `Iterator` goal is a derived obligation and the cause span carries the loop desugaring, which makes `can_be_used_for_suggestions` return false. carry the `HirId` of the iterator expression in `ObligationCauseCode::ForLoopIterator` and gate the suggestion on the span of that expression instead. rust-lang#161564

dereferencing an uncalled function only said the function type cannot be dereferenced. it now suggests the call, gated on the return type actually being dereferenceable. rust-lang#161564 (comment)

rustbot · 2026-09-01T07:28:05Z

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.

Albab-Hasan · 2026-09-01T07:29:26Z

pushed a second commit for the Deref case ais523 raised in #161564 (comment). *foo on an uncalled fn now suggests *foo(), same shape as the for loop one.

estebank · 2026-09-02T00:06:08Z

@bors r+

rust-bors · 2026-09-02T00:06:11Z

📌 Commit a97dc31 has been approved by estebank

It is now in the queue for this repository.

@oli-obk

…m-in-for-loop, r=estebank suggest calling a fn item used as the iterator of a `for` loop `suggest_fn_call` only fired when the failing obligation came from `ObligationCauseCode::FunctionArg`, so a fn item or closure used as the iterator of a `for` loop got no structured suggestion to call it. the iterator of a `for` loop is passed to `IntoIterator::into_iter`, so the failing `Iterator` goal is a derived obligation and the cause span carries the loop desugaring, which makes `can_be_used_for_suggestions` return false. carry the `HirId` of the iterator expression in `ObligationCauseCode::ForLoopIterator` and gate the suggestion on the span of that expression instead. fixes rust-lang#161564 r? @oli-obk

@oli-obk

…m-in-for-loop, r=estebank suggest calling a fn item used as the iterator of a `for` loop `suggest_fn_call` only fired when the failing obligation came from `ObligationCauseCode::FunctionArg`, so a fn item or closure used as the iterator of a `for` loop got no structured suggestion to call it. the iterator of a `for` loop is passed to `IntoIterator::into_iter`, so the failing `Iterator` goal is a derived obligation and the cause span carries the loop desugaring, which makes `can_be_used_for_suggestions` return false. carry the `HirId` of the iterator expression in `ObligationCauseCode::ForLoopIterator` and gate the suggestion on the span of that expression instead. fixes rust-lang#161564 r? @oli-obk

@oli-obk

…m-in-for-loop, r=estebank suggest calling a fn item used as the iterator of a `for` loop `suggest_fn_call` only fired when the failing obligation came from `ObligationCauseCode::FunctionArg`, so a fn item or closure used as the iterator of a `for` loop got no structured suggestion to call it. the iterator of a `for` loop is passed to `IntoIterator::into_iter`, so the failing `Iterator` goal is a derived obligation and the cause span carries the loop desugaring, which makes `can_be_used_for_suggestions` return false. carry the `HirId` of the iterator expression in `ObligationCauseCode::ForLoopIterator` and gate the suggestion on the span of that expression instead. fixes rust-lang#161564 r? @oli-obk

@oli-obk

…m-in-for-loop, r=estebank suggest calling a fn item used as the iterator of a `for` loop `suggest_fn_call` only fired when the failing obligation came from `ObligationCauseCode::FunctionArg`, so a fn item or closure used as the iterator of a `for` loop got no structured suggestion to call it. the iterator of a `for` loop is passed to `IntoIterator::into_iter`, so the failing `Iterator` goal is a derived obligation and the cause span carries the loop desugaring, which makes `can_be_used_for_suggestions` return false. carry the `HirId` of the iterator expression in `ObligationCauseCode::ForLoopIterator` and gate the suggestion on the span of that expression instead. fixes rust-lang#161564 r? @oli-obk

@oli-obk

…m-in-for-loop, r=estebank suggest calling a fn item used as the iterator of a `for` loop `suggest_fn_call` only fired when the failing obligation came from `ObligationCauseCode::FunctionArg`, so a fn item or closure used as the iterator of a `for` loop got no structured suggestion to call it. the iterator of a `for` loop is passed to `IntoIterator::into_iter`, so the failing `Iterator` goal is a derived obligation and the cause span carries the loop desugaring, which makes `can_be_used_for_suggestions` return false. carry the `HirId` of the iterator expression in `ObligationCauseCode::ForLoopIterator` and gate the suggestion on the span of that expression instead. fixes rust-lang#161564 r? @oli-obk

@oli-obk

…m-in-for-loop, r=estebank suggest calling a fn item used as the iterator of a `for` loop `suggest_fn_call` only fired when the failing obligation came from `ObligationCauseCode::FunctionArg`, so a fn item or closure used as the iterator of a `for` loop got no structured suggestion to call it. the iterator of a `for` loop is passed to `IntoIterator::into_iter`, so the failing `Iterator` goal is a derived obligation and the cause span carries the loop desugaring, which makes `can_be_used_for_suggestions` return false. carry the `HirId` of the iterator expression in `ObligationCauseCode::ForLoopIterator` and gate the suggestion on the span of that expression instead. fixes rust-lang#161564 r? @oli-obk

@oli-obk

…m-in-for-loop, r=estebank suggest calling a fn item used as the iterator of a `for` loop `suggest_fn_call` only fired when the failing obligation came from `ObligationCauseCode::FunctionArg`, so a fn item or closure used as the iterator of a `for` loop got no structured suggestion to call it. the iterator of a `for` loop is passed to `IntoIterator::into_iter`, so the failing `Iterator` goal is a derived obligation and the cause span carries the loop desugaring, which makes `can_be_used_for_suggestions` return false. carry the `HirId` of the iterator expression in `ObligationCauseCode::ForLoopIterator` and gate the suggestion on the span of that expression instead. fixes rust-lang#161564 r? @oli-obk

…uwer Rollup of 23 pull requests Successful merges: - #162164 (Revert "Implement Debug for C-like enums with a concatenated string") - #160564 (volatile: allow accesses to non-AM memory to trap) - #161579 (suggest calling a fn item used as the iterator of a `for` loop) - #162044 (coverage: Resolve spans to file-coordinates in a separate step) - #162120 (Introduce `PerOwnerLoweringState`) - #162151 (Test itanium mangling of `f16` and `f128`) - #162162 (Don't special-case `!` in stability checks anymore) - #162181 (Remove wrong UnusedBraces lint for iterator loop in edition 2024 ) - #162187 (Rename `thir::ExprKind::Use` to `ValueExpr`) - #158401 (mgca: Don't ICE when evaluating ValTrees that contain error constants) - #159873 (fuchsia: Add safestack as a supported sanitizer for x86_64 fuchsia) - #161847 (Preserve visibility in nested macro import suggestions) - #161972 (Improve tests for `#[track_caller]` in async) - #162008 (Render the `box` pattern removal diagnostic more actionable & remove `box` expression recovery) - #162065 (std: don't reference `libc::O_NOFOLLOW` on VxWorks in `set_perm_nofollow`) - #162076 (docs(num): clarify conditions under which error occurs in `impl TryFrom<int> for int`) - #162152 (Revert "retrieve supported GCC targets from the sysroot") - #162153 (Prefer `LLVMGetVersion` for runtime info) - #162168 (fix ICE in project_goals/inherent) - #162171 (Explain LoongArch f16 NaN-boxing in inline asm) - #162173 (fix supposedly unreachable `bug!` being reachable) - #162191 (core: mark float `ClampBounds` methods as `#[inline]`) - #162199 (docs(time): clarify exact seconds for hour and minute)

@oli-obk

…m-in-for-loop, r=estebank suggest calling a fn item used as the iterator of a `for` loop `suggest_fn_call` only fired when the failing obligation came from `ObligationCauseCode::FunctionArg`, so a fn item or closure used as the iterator of a `for` loop got no structured suggestion to call it. the iterator of a `for` loop is passed to `IntoIterator::into_iter`, so the failing `Iterator` goal is a derived obligation and the cause span carries the loop desugaring, which makes `can_be_used_for_suggestions` return false. carry the `HirId` of the iterator expression in `ObligationCauseCode::ForLoopIterator` and gate the suggestion on the span of that expression instead. fixes rust-lang#161564 r? @oli-obk

Rollup of 23 pull requests Successful merges: - #157808 (sanitizers: Implement support for the sanitize ignorelist) - #160564 (volatile: allow accesses to non-AM memory to trap) - #161579 (suggest calling a fn item used as the iterator of a `for` loop) - #162044 (coverage: Resolve spans to file-coordinates in a separate step) - #162120 (Introduce `PerOwnerLoweringState`) - #162151 (Test itanium mangling of `f16` and `f128`) - #162162 (Don't special-case `!` in stability checks anymore) - #162181 (Remove wrong UnusedBraces lint for iterator loop in edition 2024 ) - #162187 (Rename `thir::ExprKind::Use` to `ValueExpr`) - #158401 (mgca: Don't ICE when evaluating ValTrees that contain error constants) - #159873 (fuchsia: Add safestack as a supported sanitizer for x86_64 fuchsia) - #161847 (Preserve visibility in nested macro import suggestions) - #161972 (Improve tests for `#[track_caller]` in async) - #162008 (Render the `box` pattern removal diagnostic more actionable & remove `box` expression recovery) - #162065 (std: don't reference `libc::O_NOFOLLOW` on VxWorks in `set_perm_nofollow`) - #162076 (docs(num): clarify conditions under which error occurs in `impl TryFrom<int> for int`) - #162152 (Revert "retrieve supported GCC targets from the sysroot") - #162153 (Prefer `LLVMGetVersion` for runtime info) - #162168 (fix ICE in project_goals/inherent) - #162171 (Explain LoongArch f16 NaN-boxing in inline asm) - #162173 (fix supposedly unreachable `bug!` being reachable) - #162191 (core: mark float `ClampBounds` methods as `#[inline]`) - #162199 (docs(time): clarify exact seconds for hour and minute)

@oli-obk

…m-in-for-loop, r=estebank suggest calling a fn item used as the iterator of a `for` loop `suggest_fn_call` only fired when the failing obligation came from `ObligationCauseCode::FunctionArg`, so a fn item or closure used as the iterator of a `for` loop got no structured suggestion to call it. the iterator of a `for` loop is passed to `IntoIterator::into_iter`, so the failing `Iterator` goal is a derived obligation and the cause span carries the loop desugaring, which makes `can_be_used_for_suggestions` return false. carry the `HirId` of the iterator expression in `ObligationCauseCode::ForLoopIterator` and gate the suggestion on the span of that expression instead. fixes rust-lang#161564 r? @oli-obk

Rollup of 29 pull requests Successful merges: - #161694 (add `Complex` ABI run-make test) - #162014 (Move more `rustdoc-html` tests using `--test` into the right folder) - #162164 (Revert "Implement Debug for C-like enums with a concatenated string") - #160564 (volatile: allow accesses to non-AM memory to trap) - #161579 (suggest calling a fn item used as the iterator of a `for` loop) - #162044 (coverage: Resolve spans to file-coordinates in a separate step) - #162120 (Introduce `PerOwnerLoweringState`) - #162132 (std: improve safety documentation in UNIX stack overflow code) - #162151 (Test itanium mangling of `f16` and `f128`) - #162162 (Don't special-case `!` in stability checks anymore) - #162181 (Remove wrong UnusedBraces lint for iterator loop in edition 2024 ) - #162187 (Rename `thir::ExprKind::Use` to `ValueExpr`) - #158401 (mgca: Don't ICE when evaluating ValTrees that contain error constants) - #159873 (fuchsia: Add safestack as a supported sanitizer for x86_64 fuchsia) - #161847 (Preserve visibility in nested macro import suggestions) - #161951 (Windows: add fallback if `canonicalize` fails) - #161972 (Improve tests for `#[track_caller]` in async) - #162008 (Render the `box` pattern removal diagnostic more actionable & remove `box` expression recovery) - #162065 (std: don't reference `libc::O_NOFOLLOW` on VxWorks in `set_perm_nofollow`) - #162076 (docs(num): clarify conditions under which error occurs in `impl TryFrom<int> for int`) - #162152 (Revert "retrieve supported GCC targets from the sysroot") - #162153 (Prefer `LLVMGetVersion` for runtime info) - #162168 (fix ICE in project_goals/inherent) - #162171 (Explain LoongArch f16 NaN-boxing in inline asm) - #162173 (fix supposedly unreachable `bug!` being reachable) - #162180 (remove outdated next-solver FIXMEs) - #162191 (core: mark float `ClampBounds` methods as `#[inline]`) - #162195 (docs(time): clarify exact seconds for week and day) - #162199 (docs(time): clarify exact seconds for hour and minute)

…uwer Rollup of 25 pull requests Successful merges: - #161694 (add `Complex` ABI run-make test) - #162014 (Move more `rustdoc-html` tests using `--test` into the right folder) - #162164 (Revert "Implement Debug for C-like enums with a concatenated string") - #160564 (volatile: allow accesses to non-AM memory to trap) - #161579 (suggest calling a fn item used as the iterator of a `for` loop) - #162044 (coverage: Resolve spans to file-coordinates in a separate step) - #162120 (Introduce `PerOwnerLoweringState`) - #162132 (std: improve safety documentation in UNIX stack overflow code) - #162151 (Test itanium mangling of `f16` and `f128`) - #162162 (Don't special-case `!` in stability checks anymore) - #162181 (Remove wrong UnusedBraces lint for iterator loop in edition 2024 ) - #162187 (Rename `thir::ExprKind::Use` to `ValueExpr`) - #158401 (mgca: Don't ICE when evaluating ValTrees that contain error constants) - #159873 (fuchsia: Add safestack as a supported sanitizer for x86_64 fuchsia) - #161135 (Add `f16` and `f128` inline ASM support for PowerPC) - #161847 (Preserve visibility in nested macro import suggestions) - #161972 (Improve tests for `#[track_caller]` in async) - #162008 (Render the `box` pattern removal diagnostic more actionable & remove `box` expression recovery) - #162065 (std: don't reference `libc::O_NOFOLLOW` on VxWorks in `set_perm_nofollow`) - #162076 (docs(num): clarify conditions under which error occurs in `impl TryFrom<int> for int`) - #162111 (Update mailmap for Will Crichton and Petr Hosek) - #162152 (Revert "retrieve supported GCC targets from the sysroot") - #162153 (Prefer `LLVMGetVersion` for runtime info) - #162168 (fix ICE in project_goals/inherent) - #162171 (Explain LoongArch f16 NaN-boxing in inline asm)

@oli-obk

Rollup merge of #161579 - Albab-Hasan:suggest-calling-fn-item-in-for-loop, r=estebank suggest calling a fn item used as the iterator of a `for` loop `suggest_fn_call` only fired when the failing obligation came from `ObligationCauseCode::FunctionArg`, so a fn item or closure used as the iterator of a `for` loop got no structured suggestion to call it. the iterator of a `for` loop is passed to `IntoIterator::into_iter`, so the failing `Iterator` goal is a derived obligation and the cause span carries the loop desugaring, which makes `can_be_used_for_suggestions` return false. carry the `HirId` of the iterator expression in `ObligationCauseCode::ForLoopIterator` and gate the suggestion on the span of that expression instead. fixes #161564 r? @oli-obk

rust-timer · 2026-09-03T19:10:08Z

Note

This PR was benchmarked as part of triage of its containing rollup: triage URL.

Finished benchmarking commit (6e36ad0): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

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	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	1.8%	[1.8%, 1.8%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

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Bootstrap: missing data
Artifact size: 401.86 MiB -> 400.98 MiB (-0.22%)

…uwer Rollup of 25 pull requests Successful merges: - rust-lang/rust#161694 (add `Complex` ABI run-make test) - rust-lang/rust#162014 (Move more `rustdoc-html` tests using `--test` into the right folder) - rust-lang/rust#162164 (Revert "Implement Debug for C-like enums with a concatenated string") - rust-lang/rust#160564 (volatile: allow accesses to non-AM memory to trap) - rust-lang/rust#161579 (suggest calling a fn item used as the iterator of a `for` loop) - rust-lang/rust#162044 (coverage: Resolve spans to file-coordinates in a separate step) - rust-lang/rust#162120 (Introduce `PerOwnerLoweringState`) - rust-lang/rust#162132 (std: improve safety documentation in UNIX stack overflow code) - rust-lang/rust#162151 (Test itanium mangling of `f16` and `f128`) - rust-lang/rust#162162 (Don't special-case `!` in stability checks anymore) - rust-lang/rust#162181 (Remove wrong UnusedBraces lint for iterator loop in edition 2024 ) - rust-lang/rust#162187 (Rename `thir::ExprKind::Use` to `ValueExpr`) - rust-lang/rust#158401 (mgca: Don't ICE when evaluating ValTrees that contain error constants) - rust-lang/rust#159873 (fuchsia: Add safestack as a supported sanitizer for x86_64 fuchsia) - rust-lang/rust#161135 (Add `f16` and `f128` inline ASM support for PowerPC) - rust-lang/rust#161847 (Preserve visibility in nested macro import suggestions) - rust-lang/rust#161972 (Improve tests for `#[track_caller]` in async) - rust-lang/rust#162008 (Render the `box` pattern removal diagnostic more actionable & remove `box` expression recovery) - rust-lang/rust#162065 (std: don't reference `libc::O_NOFOLLOW` on VxWorks in `set_perm_nofollow`) - rust-lang/rust#162076 (docs(num): clarify conditions under which error occurs in `impl TryFrom<int> for int`) - rust-lang/rust#162111 (Update mailmap for Will Crichton and Petr Hosek) - rust-lang/rust#162152 (Revert "retrieve supported GCC targets from the sysroot") - rust-lang/rust#162153 (Prefer `LLVMGetVersion` for runtime info) - rust-lang/rust#162168 (fix ICE in project_goals/inherent) - rust-lang/rust#162171 (Explain LoongArch f16 NaN-boxing in inline asm)

rustbot assigned oli-obk Aug 23, 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 23, 2026

Albab-Hasan added 2 commits September 1, 2026 13:21

suggest calling a function item that is being dereferenced

a97dc31

dereferencing an uncalled function only said the function type cannot be dereferenced. it now suggests the call, gated on the return type actually being dereferenceable. rust-lang#161564 (comment)

Albab-Hasan force-pushed the suggest-calling-fn-item-in-for-loop branch from d9fc097 to a97dc31 Compare September 1, 2026 07:28

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 2, 2026

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rust-bors Bot merged commit 9d033ee into rust-lang:main Sep 3, 2026
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suggest calling a fn item used as the iterator of a `for` loop - #161579

suggest calling a fn item used as the iterator of a `for` loop#161579
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Albab-Hasan:suggest-calling-fn-item-in-for-loop

Albab-Hasan commented Aug 23, 2026 •

edited by chenyukang

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Albab-Hasan commented Aug 23, 2026 •

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