Move target checking for #[lang] to the attribute parser by JonathanBrouwer · Pull Request #158223 · rust-lang/rust

JonathanBrouwer · 2026-06-21T19:10:07Z

Work towards removing the ALL_TARGETS list.

r? @mejrs

rustbot · 2026-06-21T19:33:44Z

Some changes occurred to diagnostic attributes.

cc @mejrs

Some changes occurred in compiler/rustc_attr_parsing

cc @jdonszelmann

rustbot · 2026-06-22T15:09:52Z

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.

mejrs

Aaaaaa that '_ is very infectious.

r=me if not addressing other comment

View changes since this review

mejrs · 2026-06-23T10:10:47Z

+        let allowed_targets: &[_] = if lang_item == LangItem::PanicImpl {
+            &[Allow(Target::Fn), Allow(Target::ForeignFn)]
+        } else {
+            &[Allow(lang_item.target())]
+        };


Thoughts on changing LangItem::target to return &[Target] so that we don't need to special case PanicImpl here? Although I think I can live with this if we aren't getting more multi target lang items.

#[lang = "panic_impl"] may be gone in the near future. I have a branch to replace it with an EII. It is mostly blocked on some diagnostics improvements right now.

I did it this way because the panicimpl lang item will probably soon be replaced with EEIs.
The fact that panic_impl is valid on foreign functions at all is already a complete hack, I hope this won't be used in more places

Yeah, I expect that all future cases will either use EII or #[rustc_std_internal_symbol].

JonathanBrouwer · 2026-06-23T10:33:25Z

@bors r=mejrs rollup

rust-bors · 2026-06-23T10:33:29Z

📌 Commit 9ad6dbf has been approved by mejrs

It is now in the queue for this repository.

@mejrs

Move target checking for #[lang] to the attribute parser Work towards removing the `ALL_TARGETS` list. r? @mejrs

…uwer Rollup of 16 pull requests Successful merges: - #156885 (Fix misattributed type inference error span for index expressions) - #157271 (simplify some `proc_macro` things) - #157883 (Remove strict invariant node_type on hir_type during ty privacy visit) - #157921 (trait solver: Resolve region vars in max universe) - #157960 (delegation: add support for infers in generics) - #158105 (Extract all instance shim variants into new `ShimKind` enum) - #158207 (Resolver: local/external split of `resolve_ident_in_module_non_globs_unadjusted` ) - #158279 (Follow goto and drop when linting unreachable code) - #157807 (don't ice on non-lifetime binders under `-Zassumptions-on-binders`) - #158020 (Update mingw-w64 C toolchain) - #158222 (format: ignore println newline in foreign format hints) - #158223 (Move target checking for #[lang] to the attribute parser) - #158252 (Use `cfg_select` in `std::os`) - #158257 ( fix escaping placeholder check in next solver normalization folder) - #158274 (triagebot: Stop pinging myself) - #158282 (slice_split_once: bounds check optimization note) Failed merges: - #158256 (Avoid parser panics bubbling out to proc macros)

@mejrs

Move target checking for #[lang] to the attribute parser Work towards removing the `ALL_TARGETS` list. r? @mejrs

@mejrs

Move target checking for #[lang] to the attribute parser Work towards removing the `ALL_TARGETS` list. r? @mejrs

…uwer Rollup of 23 pull requests Successful merges: - #158315 (`rust-analyzer` subtree update) - #155739 (Add temporary scope to assert_eq and assert_ne) - #156885 (Fix misattributed type inference error span for index expressions) - #157271 (simplify some `proc_macro` things) - #157883 (Remove strict invariant node_type on hir_type during ty privacy visit) - #157921 (trait solver: Resolve region vars in max universe) - #157960 (delegation: add support for infers in generics) - #157983 (Lift the same-signature restriction for `extern "tail"`) - #158105 (Extract all instance shim variants into new `ShimKind` enum) - #158207 (Resolver: local/external split of `resolve_ident_in_module_non_globs_unadjusted` ) - #158279 (Follow goto and drop when linting unreachable code) - #157527 (Move derive tests into their dedicated folder) - #157807 (don't ice on non-lifetime binders under `-Zassumptions-on-binders`) - #158020 (Update mingw-w64 C toolchain) - #158222 (format: ignore println newline in foreign format hints) - #158223 (Move target checking for #[lang] to the attribute parser) - #158252 (Use `cfg_select` in `std::os`) - #158257 ( fix escaping placeholder check in next solver normalization folder) - #158263 (Only load the feature list once in the entire resolver) - #158274 (triagebot: Stop pinging myself) - #158282 (slice_split_once: bounds check optimization note) - #158300 (Improve unknown crate_type diagnostic suggestions) - #158304 (mailmap: update mu001999) Failed merges: - #158256 (Avoid parser panics bubbling out to proc macros)

@mejrs

Move target checking for #[lang] to the attribute parser Work towards removing the `ALL_TARGETS` list. r? @mejrs

Rollup of 27 pull requests Successful merges: - #158315 (`rust-analyzer` subtree update) - #155739 (Add temporary scope to assert_eq and assert_ne) - #156885 (Fix misattributed type inference error span for index expressions) - #157271 (simplify some `proc_macro` things) - #157883 (Remove strict invariant node_type on hir_type during ty privacy visit) - #157921 (trait solver: Resolve region vars in max universe) - #157960 (delegation: add support for infers in generics) - #157983 (Lift the same-signature restriction for `extern "tail"`) - #158053 (Optimize network address parser) - #158105 (Extract all instance shim variants into new `ShimKind` enum) - #158207 (Resolver: local/external split of `resolve_ident_in_module_non_globs_unadjusted` ) - #158279 (Follow goto and drop when linting unreachable code) - #157527 (Move derive tests into their dedicated folder) - #157807 (don't ice on non-lifetime binders under `-Zassumptions-on-binders`) - #158020 (Update mingw-w64 C toolchain) - #158039 (c-variadic: test that we use equality up to free lifetimes) - #158222 (format: ignore println newline in foreign format hints) - #158223 (Move target checking for #[lang] to the attribute parser) - #158252 (Use `cfg_select` in `std::os`) - #158257 ( fix escaping placeholder check in next solver normalization folder) - #158263 (Only load the feature list once in the entire resolver) - #158267 (FromUtf8Error::into_utf8_lossy better example and suggest use) - #158274 (triagebot: Stop pinging myself) - #158282 (slice_split_once: bounds check optimization note) - #158300 (Improve unknown crate_type diagnostic suggestions) - #158304 (mailmap: update mu001999) - #158309 (Update `rustc-literal-escaper` version to `0.0.8`) Failed merges: - #158256 (Avoid parser panics bubbling out to proc macros)

@mejrs

Move target checking for #[lang] to the attribute parser Work towards removing the `ALL_TARGETS` list. r? @mejrs

Rollup of 35 pull requests Successful merges: - #158315 (`rust-analyzer` subtree update) - #158336 (Stop excluding `stdarch` test crates from `rust-src`) - #155739 (Add temporary scope to assert_eq and assert_ne) - #156885 (Fix misattributed type inference error span for index expressions) - #157271 (simplify some `proc_macro` things) - #157419 (move rustc_type_ir Term things to term_kind.rs) - #157883 (Remove strict invariant node_type on hir_type during ty privacy visit) - #157921 (trait solver: Resolve region vars in max universe) - #157960 (delegation: add support for infers in generics) - #157983 (Lift the same-signature restriction for `extern "tail"`) - #158053 (Optimize network address parser) - #158105 (Extract all instance shim variants into new `ShimKind` enum) - #158207 (Resolver: local/external split of `resolve_ident_in_module_non_globs_unadjusted` ) - #158279 (Follow goto and drop when linting unreachable code) - #157527 (Move derive tests into their dedicated folder) - #157807 (don't ice on non-lifetime binders under `-Zassumptions-on-binders`) - #157939 (Reorganize `tests/ui/issues` [8/N]) - #157946 (Make `char::is_private_use` and `char::is_assigned` unstably public) - #158003 (Reorganize `tests/ui/issues` [9/N]) - #158020 (Update mingw-w64 C toolchain) - #158039 (c-variadic: test that we use equality up to free lifetimes) - #158060 (Reorganize `tests/ui/issues` [10/N]) - #158222 (format: ignore println newline in foreign format hints) - #158223 (Move target checking for #[lang] to the attribute parser) - #158252 (Use `cfg_select` in `std::os`) - #158263 (Only load the feature list once in the entire resolver) - #158267 (FromUtf8Error::into_utf8_lossy better example and suggest use) - #158272 (Reorganize `tests/ui/issues` [13/N]) - #158274 (triagebot: Stop pinging myself) - #158282 (slice_split_once: bounds check optimization note) - #158300 (Improve unknown crate_type diagnostic suggestions) - #158304 (mailmap: update mu001999) - #158309 (Update `rustc-literal-escaper` version to `0.0.8`) - #158314 (Fix incorrect unsafe debug assertion in unchecked_div_exact) - #158326 (Add `io::ErrorKind::TooManyOpenFiles`)

@mejrs

Move target checking for #[lang] to the attribute parser Work towards removing the `ALL_TARGETS` list. r? @mejrs

Rollup of 35 pull requests Successful merges: - #158315 (`rust-analyzer` subtree update) - #158336 (Stop excluding `stdarch` test crates from `rust-src`) - #155739 (Add temporary scope to assert_eq and assert_ne) - #156885 (Fix misattributed type inference error span for index expressions) - #157271 (simplify some `proc_macro` things) - #157419 (move rustc_type_ir Term things to term_kind.rs) - #157883 (Remove strict invariant node_type on hir_type during ty privacy visit) - #157921 (trait solver: Resolve region vars in max universe) - #157960 (delegation: add support for infers in generics) - #157983 (Lift the same-signature restriction for `extern "tail"`) - #158053 (Optimize network address parser) - #158105 (Extract all instance shim variants into new `ShimKind` enum) - #158207 (Resolver: local/external split of `resolve_ident_in_module_non_globs_unadjusted` ) - #158279 (Follow goto and drop when linting unreachable code) - #157527 (Move derive tests into their dedicated folder) - #157807 (don't ice on non-lifetime binders under `-Zassumptions-on-binders`) - #157939 (Reorganize `tests/ui/issues` [8/N]) - #157946 (Make `char::is_private_use` and `char::is_assigned` unstably public) - #158003 (Reorganize `tests/ui/issues` [9/N]) - #158020 (Update mingw-w64 C toolchain) - #158039 (c-variadic: test that we use equality up to free lifetimes) - #158060 (Reorganize `tests/ui/issues` [10/N]) - #158222 (format: ignore println newline in foreign format hints) - #158223 (Move target checking for #[lang] to the attribute parser) - #158252 (Use `cfg_select` in `std::os`) - #158263 (Only load the feature list once in the entire resolver) - #158267 (FromUtf8Error::into_utf8_lossy better example and suggest use) - #158272 (Reorganize `tests/ui/issues` [13/N]) - #158274 (triagebot: Stop pinging myself) - #158282 (slice_split_once: bounds check optimization note) - #158300 (Improve unknown crate_type diagnostic suggestions) - #158304 (mailmap: update mu001999) - #158309 (Update `rustc-literal-escaper` version to `0.0.8`) - #158314 (Fix incorrect unsafe debug assertion in unchecked_div_exact) - #158326 (Add `io::ErrorKind::TooManyOpenFiles`)

@mejrs

Rollup merge of #158223 - JonathanBrouwer:lang-target, r=mejrs Move target checking for #[lang] to the attribute parser Work towards removing the `ALL_TARGETS` list. r? @mejrs

JonathanBrouwer · 2026-06-25T10:56:32Z

@rust-timer build 1555e18
Perf run for #158342

rust-timer · 2026-06-25T18:42:31Z

Finished benchmarking commit (1555e18): comparison URL.

Overall result: ❌✅ regressions and improvements - no action needed

Benchmarking means the PR may be perf-sensitive. Consider adding rollup=never if this change is not fit for rolling up.

@rustbot label: -S-waiting-on-perf -perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.4%	[0.4%, 0.4%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.2%	[-0.2%, -0.2%]	1
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary 4.7%, secondary -2.7%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	4.7%	[4.7%, 4.7%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.7%	[-2.7%, -2.7%]	1
All ❌✅ (primary)	4.7%	[4.7%, 4.7%]	1

Cycles

Results (secondary 12.0%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	12.0%	[2.3%, 21.7%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

This perf run didn't have relevant results for this metric.

Bootstrap: 503.101s -> 504.026s (0.18%)
Artifact size: 353.51 MiB -> 353.59 MiB (0.02%)

Rollup of 35 pull requests Successful merges: - rust-lang/rust#158315 (`rust-analyzer` subtree update) - rust-lang/rust#158336 (Stop excluding `stdarch` test crates from `rust-src`) - rust-lang/rust#155739 (Add temporary scope to assert_eq and assert_ne) - rust-lang/rust#156885 (Fix misattributed type inference error span for index expressions) - rust-lang/rust#157271 (simplify some `proc_macro` things) - rust-lang/rust#157419 (move rustc_type_ir Term things to term_kind.rs) - rust-lang/rust#157883 (Remove strict invariant node_type on hir_type during ty privacy visit) - rust-lang/rust#157921 (trait solver: Resolve region vars in max universe) - rust-lang/rust#157960 (delegation: add support for infers in generics) - rust-lang/rust#157983 (Lift the same-signature restriction for `extern "tail"`) - rust-lang/rust#158053 (Optimize network address parser) - rust-lang/rust#158105 (Extract all instance shim variants into new `ShimKind` enum) - rust-lang/rust#158207 (Resolver: local/external split of `resolve_ident_in_module_non_globs_unadjusted` ) - rust-lang/rust#158279 (Follow goto and drop when linting unreachable code) - rust-lang/rust#157527 (Move derive tests into their dedicated folder) - rust-lang/rust#157807 (don't ice on non-lifetime binders under `-Zassumptions-on-binders`) - rust-lang/rust#157939 (Reorganize `tests/ui/issues` [8/N]) - rust-lang/rust#157946 (Make `char::is_private_use` and `char::is_assigned` unstably public) - rust-lang/rust#158003 (Reorganize `tests/ui/issues` [9/N]) - rust-lang/rust#158020 (Update mingw-w64 C toolchain) - rust-lang/rust#158039 (c-variadic: test that we use equality up to free lifetimes) - rust-lang/rust#158060 (Reorganize `tests/ui/issues` [10/N]) - rust-lang/rust#158222 (format: ignore println newline in foreign format hints) - rust-lang/rust#158223 (Move target checking for #[lang] to the attribute parser) - rust-lang/rust#158252 (Use `cfg_select` in `std::os`) - rust-lang/rust#158263 (Only load the feature list once in the entire resolver) - rust-lang/rust#158267 (FromUtf8Error::into_utf8_lossy better example and suggest use) - rust-lang/rust#158272 (Reorganize `tests/ui/issues` [13/N]) - rust-lang/rust#158274 (triagebot: Stop pinging myself) - rust-lang/rust#158282 (slice_split_once: bounds check optimization note) - rust-lang/rust#158300 (Improve unknown crate_type diagnostic suggestions) - rust-lang/rust#158304 (mailmap: update mu001999) - rust-lang/rust#158309 (Update `rustc-literal-escaper` version to `0.0.8`) - rust-lang/rust#158314 (Fix incorrect unsafe debug assertion in unchecked_div_exact) - rust-lang/rust#158326 (Add `io::ErrorKind::TooManyOpenFiles`)

oli-obk · 2026-07-09T09:33:25Z

+                    if actual_target != lang_item.target() {
+                        self.tcx
+                            .dcx()
+                            .delayed_bug("lang item target is checked in attribute parser");


the attr parser only checks that the lang item attr is applied to a valid target, not that it is applied to the correct target for this lang item. I just hit this delayed bug when using the wrong target

View changes since the review

or the attr parser is too lenient. I used a foreign fn instead of a fn, and that blew up

What lang item did you try to use?

rustbot added A-attributes Area: Attributes (`#[…]`, `#![…]`) S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Jun 21, 2026

JonathanBrouwer force-pushed the lang-target branch from d920642 to 6f84b3b Compare June 21, 2026 19:32

rustbot assigned mejrs Jun 21, 2026

JonathanBrouwer marked this pull request as ready for review June 21, 2026 19:33

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 Jun 21, 2026

JonathanBrouwer force-pushed the lang-target branch from 6f84b3b to dfb0455 Compare June 21, 2026 19:41

This comment has been minimized.

Sign in to view

bjorn3 reviewed Jun 22, 2026

View reviewed changes

Comment thread compiler/rustc_passes/src/lang_items.rs Outdated

bjorn3 reviewed Jun 22, 2026

View reviewed changes

Comment thread compiler/rustc_passes/src/lang_items.rs

JonathanBrouwer added 3 commits June 22, 2026 17:09

Move target checking for #[lang] to the attribute parser

f99e894

Add lifetime parameter to AllowedTargets

b8758a3

Use AllowedTargets::ManuallyChecked for LangParser

9ad6dbf

JonathanBrouwer force-pushed the lang-target branch from dfb0455 to 9ad6dbf Compare June 22, 2026 15:09

mejrs approved these changes Jun 23, 2026

View reviewed changes

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 Jun 23, 2026

JonathanBrouwer mentioned this pull request Jun 23, 2026

Rollup of 16 pull requests #158301

Closed

JonathanBrouwer mentioned this pull request Jun 23, 2026

Rollup of 23 pull requests #158316

Closed

JonathanBrouwer mentioned this pull request Jun 23, 2026

Rollup of 23 pull requests #158324

Closed

jhpratt added a commit to jhpratt/rust that referenced this pull request Jun 24, 2026

Rollup merge of rust-lang#158223 - JonathanBrouwer:lang-target, r=mejrs

399855f

Move target checking for #[lang] to the attribute parser Work towards removing the `ALL_TARGETS` list. r? @mejrs

jhpratt mentioned this pull request Jun 24, 2026

Rollup of 27 pull requests #158335

Closed

jhpratt added a commit to jhpratt/rust that referenced this pull request Jun 24, 2026

Rollup merge of rust-lang#158223 - JonathanBrouwer:lang-target, r=mejrs

fe2bfaf

Move target checking for #[lang] to the attribute parser Work towards removing the `ALL_TARGETS` list. r? @mejrs

This was referenced Jun 24, 2026

Rollup of 34 pull requests #158337

Closed

Rollup of 35 pull requests #158342

Merged

JonathanBrouwer mentioned this pull request Jun 24, 2026

[CI] Rollup of 35 pull requests #158354

Closed

rust-bors Bot merged commit df53430 into rust-lang:main Jun 25, 2026
13 checks passed

rustbot added this to the 1.98.0 milestone Jun 25, 2026

rust-timer added a commit that referenced this pull request Jun 25, 2026

Unrolled build for #158223

1555e18

Rollup merge of #158223 - JonathanBrouwer:lang-target, r=mejrs Move target checking for #[lang] to the attribute parser Work towards removing the `ALL_TARGETS` list. r? @mejrs

This comment has been minimized.

Sign in to view

oli-obk reviewed Jul 9, 2026

View reviewed changes

Uh oh!

Uh oh!

Conversation

JonathanBrouwer commented Jun 21, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

rustbot commented Jun 21, 2026

Uh oh!

This comment has been minimized.

Uh oh!

Uh oh!

rustbot commented Jun 22, 2026

Uh oh!

mejrs left a comment • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

JonathanBrouwer Jun 23, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

JonathanBrouwer commented Jun 23, 2026

Uh oh!

rust-bors Bot commented Jun 23, 2026

Uh oh!

Uh oh!

JonathanBrouwer commented Jun 25, 2026

Uh oh!

This comment has been minimized.

rust-timer commented Jun 25, 2026

Overall result: ❌✅ regressions and improvements - no action needed

Uh oh!

oli-obk Jul 9, 2026 • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

6 participants

JonathanBrouwer commented Jun 21, 2026 •

edited

Loading

mejrs left a comment •

edited by rustbot

Loading

JonathanBrouwer Jun 23, 2026 •

edited

Loading

oli-obk Jul 9, 2026 •

edited by rustbot

Loading