parse `const trait Trait` #143879

fee1-dead · 2025-07-13T10:09:25Z

r? oli-obk or anyone from project-const-traits

cc @rust-lang/project-const-traits

rustbot · 2025-07-13T10:09:31Z

The rustc-dev-guide subtree was changed. If this PR only touches the dev guide consider submitting a PR directly to rust-lang/rustc-dev-guide otherwise thank you for updating the dev guide with your changes.

cc @BoxyUwU, @jieyouxu, @Kobzol, @tshepang

This PR changes a file inside tests/crashes. If a crash was fixed, please move into the corresponding ui subdir and add 'Fixes #' to the PR description to autoclose the issue upon merge.

Some changes occurred to the CTFE machinery

cc @RalfJung, @oli-obk, @lcnr

Some changes occurred in src/tools/clippy

cc @rust-lang/clippy

HIR ty lowering was modified

cc @fmease

Some changes occurred in src/tools/rustfmt

cc @rust-lang/rustfmt

Some changes occurred in compiler/rustc_attr_parsing

cc @jdonszelmann

rust-analyzer is developed in its own repository. If possible, consider making this change to rust-lang/rust-analyzer instead.

cc @rust-lang/rust-analyzer

Some changes occurred in compiler/rustc_passes/src/check_attr.rs

cc @jdonszelmann

rustbot · 2025-07-13T15:54:03Z

This PR modifies run-make tests.

cc @jieyouxu

bors · 2025-07-13T19:39:08Z

☔ The latest upstream changes (presumably #143888) made this pull request unmergeable. Please resolve the merge conflicts.

fmease · 2025-07-13T23:50:20Z

compiler/rustc_parse/src/parser/item.rs

+            || self.check_keyword(exp!(Const)) && (self.is_keyword_ahead(1, &[kw::Trait])
+                || self.is_keyword_ahead(1, &[kw::Unsafe]) && self.is_keyword_ahead(2, &[kw::Trait, kw::Auto]))


This doesn't admit const auto trait Trait {}, it should tho (it already allows const unsafe auto trait Trait {}). Ofc for that const auto needs to be followed by trait so we don't regress const auto: () = ();.

fmease

Looks good, thanks! r=me after rebase, fmt fix and with nits addressed.

fmease · 2025-07-13T23:59:26Z

src/tools/rust-analyzer/crates/test-utils/src/minicore.rs

I don't think this file should be modified? This will just fail in r-a's repo after the sync bc r-a doesn't impl the new syntax (we currently don't run r-a's tests in r-l/r's CI).

I think it's fine, we actually parse const trait and the tests still run with that change.

fee1-dead · 2025-07-14T08:17:08Z

r? fmease
@bors r=fmease

bors · 2025-07-14T08:17:10Z

📌 Commit 124c33e has been approved by fmease

It is now in the queue for this repository.

rustbot · 2025-07-14T08:17:11Z

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

…y, r=fmease parse `const trait Trait` r? oli-obk or anyone from project-const-traits cc ``@rust-lang/project-const-traits``

fmease · 2025-07-17T08:56:05Z

@bors p=1 bitrotty

fmease · 2025-07-17T12:07:20Z

@bors r+

bors · 2025-07-17T12:07:22Z

📌 Commit 6932687 has been approved by fmease

It is now in the queue for this repository.

…y, r=fmease parse `const trait Trait` r? oli-obk or anyone from project-const-traits cc `@rust-lang/project-const-traits`

…y, r=fmease parse `const trait Trait` r? oli-obk or anyone from project-const-traits cc ``@rust-lang/project-const-traits``

Rollup of 15 pull requests Successful merges: - #142300 (Disable `tests/run-make/mte-ffi` because no CI runners have MTE extensions enabled) - #143271 (Store the type of each GVN value) - #143293 (fix `-Zsanitizer=kcfi` on `#[naked]` functions) - #143719 (Emit warning when there is no space between `-o` and arg) - #143833 (Ban projecting into SIMD types [MCP838]) - #143846 (pass --gc-sections if -Zexport-executable-symbols is enabled and improve tests) - #143879 (parse `const trait Trait`) - #143891 (Port `#[coverage]` to the new attribute system) - #143967 (constify `Option` methods) - #143985 (rustc_public: de-StableMIR-ize) - #144008 (Fix false positive double negations with macro invocation) - #144010 (Boostrap: add warning on `optimize = false`) - #144034 (tests: Test line number in debuginfo for diverging function calls) - #144049 (rustc-dev-guide subtree update) - #144056 (Copy GCC sources into the build directory even outside CI) r? `@ghost` `@rustbot` modify labels: rollup

bors · 2025-07-17T15:54:36Z

⌛ Testing commit 6932687 with merge 9cd918b...

bors · 2025-07-17T18:59:23Z

☀️ Test successful - checks-actions
Approved by: fmease
Pushing 9cd918b to master...

github-actions · 2025-07-17T19:02:20Z

What is this?

This is an experimental post-merge analysis report that shows differences in test outcomes between the merged PR and its parent PR.

Comparing bf5e6cc (parent) -> 9cd918b (this PR)

Test differences

Show 214 test diffs

Stage 1

errors::verify_parse_array_index_offset_of_167: pass -> [missing] (J0)
errors::verify_parse_array_index_offset_of_168: [missing] -> pass (J0)
errors::verify_parse_asm_expected_comma_180: pass -> [missing] (J0)
errors::verify_parse_asm_expected_comma_181: [missing] -> pass (J0)
errors::verify_parse_asm_expected_other_181: pass -> [missing] (J0)
errors::verify_parse_asm_expected_string_literal_183: pass -> [missing] (J0)
errors::verify_parse_asm_expected_string_literal_184: [missing] -> pass (J0)
errors::verify_parse_asm_non_abi_182: pass -> [missing] (J0)
errors::verify_parse_asm_non_abi_183: [missing] -> pass (J0)
errors::verify_parse_asm_requires_template_179: pass -> [missing] (J0)
errors::verify_parse_asm_requires_template_180: [missing] -> pass (J0)
errors::verify_parse_asm_sym_no_path_178: pass -> [missing] (J0)
errors::verify_parse_asm_underscore_input_177: pass -> [missing] (J0)
errors::verify_parse_associated_static_item_not_allowed_86: [missing] -> pass (J0)
errors::verify_parse_async_impl_169: pass -> [missing] (J0)
errors::verify_parse_at_dot_dot_in_struct_pattern_125: pass -> [missing] (J0)
errors::verify_parse_at_dot_dot_in_struct_pattern_126: [missing] -> pass (J0)
errors::verify_parse_at_in_struct_pattern_126: pass -> [missing] (J0)
errors::verify_parse_attr_after_generic_141: pass -> [missing] (J0)
errors::verify_parse_attr_after_generic_142: [missing] -> pass (J0)
errors::verify_parse_bad_assoc_type_bounds_140: pass -> [missing] (J0)
errors::verify_parse_bad_item_kind_152: pass -> [missing] (J0)
errors::verify_parse_bad_item_kind_153: [missing] -> pass (J0)
errors::verify_parse_bad_return_type_notation_output_139: pass -> [missing] (J0)
errors::verify_parse_bad_return_type_notation_output_140: [missing] -> pass (J0)
errors::verify_parse_binder_and_polarity_175: [missing] -> pass (J0)
errors::verify_parse_binder_before_modifiers_174: [missing] -> pass (J0)
errors::verify_parse_cannot_be_raw_ident_104: [missing] -> pass (J0)
errors::verify_parse_const_global_cannot_be_mutable_88: [missing] -> pass (J0)
errors::verify_parse_cr_doc_comment_108: [missing] -> pass (J0)
errors::verify_parse_dyn_after_mut_135: [missing] -> pass (J0)
errors::verify_parse_empty_exponent_float_110: pass -> [missing] (J0)
errors::verify_parse_empty_exponent_float_111: [missing] -> pass (J0)
errors::verify_parse_enum_pattern_instead_of_identifier_124: pass -> [missing] (J0)
errors::verify_parse_enum_pattern_instead_of_identifier_125: [missing] -> pass (J0)
errors::verify_parse_enum_struct_mutually_exclusive_89: pass -> [missing] (J0)
errors::verify_parse_expect_label_found_ident_148: pass -> [missing] (J0)
errors::verify_parse_expected_binding_left_of_at_118: pass -> [missing] (J0)
errors::verify_parse_expected_builtin_ident_164: pass -> [missing] (J0)
errors::verify_parse_expected_builtin_ident_165: [missing] -> pass (J0)
errors::verify_parse_expected_comma_after_pattern_field_128: pass -> [missing] (J0)
errors::verify_parse_expected_mut_or_const_in_raw_pointer_type_132: pass -> [missing] (J0)
errors::verify_parse_extern_item_cannot_be_const_86: pass -> [missing] (J0)
errors::verify_parse_float_literal_unsupported_base_111: pass -> [missing] (J0)
errors::verify_parse_fn_pointer_cannot_be_async_137: [missing] -> pass (J0)
errors::verify_parse_fn_pointer_cannot_be_const_135: pass -> [missing] (J0)
errors::verify_parse_fn_pointer_cannot_be_const_136: [missing] -> pass (J0)
errors::verify_parse_generic_args_in_pat_require_turbofish_syntax_166: pass -> [missing] (J0)
errors::verify_parse_generic_args_in_pat_require_turbofish_syntax_167: [missing] -> pass (J0)
errors::verify_parse_inappropriate_default_149: pass -> [missing] (J0)
errors::verify_parse_inappropriate_default_150: [missing] -> pass (J0)
errors::verify_parse_invalid_attr_unsafe_172: pass -> [missing] (J0)
errors::verify_parse_invalid_digit_literal_109: pass -> [missing] (J0)
errors::verify_parse_invalid_offset_of_168: pass -> [missing] (J0)
errors::verify_parse_invalid_offset_of_169: [missing] -> pass (J0)
errors::verify_parse_keyword_lifetime_105: pass -> [missing] (J0)
errors::verify_parse_keyword_lifetime_106: [missing] -> pass (J0)
errors::verify_parse_lifetime_in_eq_constraint_145: pass -> [missing] (J0)
errors::verify_parse_lifetime_in_eq_constraint_146: [missing] -> pass (J0)
errors::verify_parse_macro_invocation_visibility_157: [missing] -> pass (J0)
errors::verify_parse_macro_name_remove_bang_155: [missing] -> pass (J0)
errors::verify_parse_macro_rules_visibility_155: pass -> [missing] (J0)
errors::verify_parse_macro_rules_visibility_156: [missing] -> pass (J0)
errors::verify_parse_malformed_cfg_attr_163: [missing] -> pass (J0)
errors::verify_parse_missing_const_type_89: [missing] -> pass (J0)
errors::verify_parse_missing_plus_in_bounds_160: pass -> [missing] (J0)
errors::verify_parse_missing_plus_in_bounds_161: [missing] -> pass (J0)
errors::verify_parse_modifier_lifetime_146: pass -> [missing] (J0)
errors::verify_parse_multiple_where_clauses_99: [missing] -> pass (J0)
errors::verify_parse_mut_on_nested_ident_pattern_120: pass -> [missing] (J0)
errors::verify_parse_mut_on_non_ident_pattern_121: pass -> [missing] (J0)
errors::verify_parse_need_plus_after_trait_object_lifetime_131: pass -> [missing] (J0)
errors::verify_parse_nested_c_variadic_type_138: [missing] -> pass (J0)
errors::verify_parse_nonterminal_expected_ident_101: pass -> [missing] (J0)
errors::verify_parse_nonterminal_expected_ident_102: [missing] -> pass (J0)
errors::verify_parse_nonterminal_expected_item_keyword_99: pass -> [missing] (J0)
errors::verify_parse_nonterminal_expected_statement_101: [missing] -> pass (J0)
errors::verify_parse_pattern_on_wrong_side_of_at_117: pass -> [missing] (J0)
errors::verify_parse_pattern_on_wrong_side_of_at_118: [missing] -> pass (J0)
errors::verify_parse_recover_import_as_use_150: pass -> [missing] (J0)
errors::verify_parse_repeated_mut_in_pattern_122: pass -> [missing] (J0)
errors::verify_parse_return_types_use_thin_arrow_130: pass -> [missing] (J0)
errors::verify_parse_single_colon_import_path_152: [missing] -> pass (J0)
errors::verify_parse_static_with_generics_166: [missing] -> pass (J0)
errors::verify_parse_trailing_vert_not_allowed_116: [missing] -> pass (J0)
errors::verify_parse_trait_alias_cannot_be_const_84: [missing] -> pass (J0)
errors::verify_parse_underscore_literal_suffix_148: [missing] -> pass (J0)
errors::verify_parse_unexpected_expr_in_pat_129: pass -> [missing] (J0)
errors::verify_parse_unexpected_lifetime_in_pattern_119: pass -> [missing] (J0)
errors::verify_parse_unexpected_self_in_generic_parameters_97: [missing] -> pass (J0)
errors::verify_parse_unexpected_token_after_struct_name_found_doc_comment_93: pass -> [missing] (J0)
errors::verify_parse_unexpected_token_after_struct_name_found_doc_comment_94: [missing] -> pass (J0)
errors::verify_parse_unexpected_token_after_struct_name_found_keyword_91: pass -> [missing] (J0)
errors::verify_parse_unexpected_token_after_struct_name_found_keyword_92: [missing] -> pass (J0)
errors::verify_parse_unexpected_token_after_struct_name_found_reserved_identifier_90: pass -> [missing] (J0)
errors::verify_parse_unexpected_vert_vert_before_function_parameter_114: [missing] -> pass (J0)
errors::verify_parse_unexpected_vert_vert_in_pattern_114: pass -> [missing] (J0)
errors::verify_parse_unexpected_vert_vert_in_pattern_115: [missing] -> pass (J0)
errors::verify_parse_unknown_builtin_construct_164: [missing] -> pass (J0)
errors::verify_parse_unmatched_angle_160: [missing] -> pass (J0)

(and 103 additional test diffs)

Additionally, 11 doctest diffs were found. These are ignored, as they are noisy.

Job group index

J0: aarch64-apple, aarch64-gnu, aarch64-msvc-2, i686-gnu-2, i686-gnu-nopt-2, i686-msvc-2, x86_64-apple-1, x86_64-gnu, x86_64-gnu-llvm-19-1, x86_64-gnu-llvm-19-3, x86_64-gnu-llvm-20-1, x86_64-gnu-llvm-20-3, x86_64-gnu-nopt, x86_64-gnu-stable, x86_64-mingw-2, x86_64-msvc-2

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard 9cd918bcbbc26deb005eb4e1bd9a445380195e56 --output-dir test-dashboard

And then open test-dashboard/index.html in your browser to see an overview of all executed tests.

Job duration changes

dist-aarch64-linux: 7925.3s -> 6016.6s (-24.1%)
dist-x86_64-apple: 10769.6s -> 8804.6s (-18.2%)
pr-check-1: 1765.2s -> 1564.7s (-11.4%)
tidy: 63.6s -> 70.6s (10.8%)
x86_64-apple-2: 5262.8s -> 4760.6s (-9.5%)
aarch64-apple: 4054.6s -> 4395.7s (8.4%)
dist-x86_64-netbsd: 4614.1s -> 4993.3s (8.2%)
dist-aarch64-windows-gnullvm: 4415.9s -> 4742.6s (7.4%)
dist-aarch64-msvc: 4678.7s -> 5015.4s (7.2%)
dist-powerpc-linux: 4947.7s -> 5286.3s (6.8%)

How to interpret the job duration changes?

Job durations can vary a lot, based on the actual runner instance
that executed the job, system noise, invalidated caches, etc. The table above is provided
mostly for t-infra members, for simpler debugging of potential CI slow-downs.

rust-timer · 2025-07-17T20:17:15Z

Finished benchmarking commit (9cd918b): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results (primary -3.0%, secondary -1.5%)

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)	2.4%	[2.4%, 2.4%]	1
Improvements ✅ (primary)	-3.0%	[-3.5%, -2.5%]	2
Improvements ✅ (secondary)	-3.4%	[-4.2%, -2.6%]	2
All ❌✅ (primary)	-3.0%	[-3.5%, -2.5%]	2

Cycles

Results (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)	-	-	0
Regressions ❌ (secondary)	2.7%	[2.7%, 2.7%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 464.659s -> 464.098s (-0.12%)
Artifact size: 374.78 MiB -> 374.74 MiB (-0.01%)

… r=fmease parse `const trait Trait` r? oli-obk or anyone from project-const-traits cc `@rust-lang/project-const-traits`

ytmimi · 2025-07-31T21:12:45Z

src/tools/rustfmt/src/items.rs

-        "{}{}{}trait ",
+        "{}{}{}{}trait ",
+        format_constness(constness),


rust-lang/rustfmt#6619 was recently opened. @fee1-dead I think the formatting with regards to visibility is incorrect. I tested this with rustfmt 1.8.0-nightly (3048886 2025-07-30)

…BoxyUwU Gate const trait syntax Missed this during my review of rust-lang#143879, huge apologies! Fixes [after beta backport] rust-lang#144958. cc ``@fee1-dead`` r? ``@BoxyUwU`` or anyone

Rollup merge of #144956 - fmease:gate-const-trait-syntax, r=BoxyUwU Gate const trait syntax Missed this during my review of #143879, huge apologies! Fixes [after beta backport] #144958. cc ``@fee1-dead`` r? ``@BoxyUwU`` or anyone

rustbot assigned oli-obk Jul 13, 2025

fee1-dead added the F-const_trait_impl `#![feature(const_trait_impl)]` label Jul 13, 2025

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fee1-dead force-pushed the push-lrlpoouyqqry branch from fbc7508 to 49ab742 Compare July 13, 2025 12:08

rustbot added the T-clippy Relevant to the Clippy team. label Jul 13, 2025

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fee1-dead force-pushed the push-lrlpoouyqqry branch from 4e9b986 to b782ee2 Compare July 13, 2025 15:54

rustbot added the A-run-make Area: port run-make Makefiles to rmake.rs label Jul 13, 2025

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fmease reviewed Jul 13, 2025

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fmease approved these changes Jul 14, 2025

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fee1-dead force-pushed the push-lrlpoouyqqry branch from b782ee2 to 124c33e Compare July 14, 2025 06:31

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bors removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jul 14, 2025

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bors added the S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. label Jul 14, 2025

parse const trait Trait

6932687

fee1-dead force-pushed the push-lrlpoouyqqry branch from f62b29b to 6932687 Compare July 17, 2025 10:07

bors 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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jul 17, 2025

fmease added a commit to fmease/rust that referenced this pull request Jul 17, 2025

Rollup merge of rust-lang#143879 - fee1-dead-contrib:push-lrlpoouyqqr…

bd2ef4a

…y, r=fmease parse `const trait Trait` r? oli-obk or anyone from project-const-traits cc `@rust-lang/project-const-traits`

fmease mentioned this pull request Jul 17, 2025

Rollup of 16 pull requests #144067

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fmease added a commit to fmease/rust that referenced this pull request Jul 17, 2025

Rollup merge of rust-lang#143879 - fee1-dead-contrib:push-lrlpoouyqqr…

1b8b8af

…y, r=fmease parse `const trait Trait` r? oli-obk or anyone from project-const-traits cc ``@rust-lang/project-const-traits``

fmease mentioned this pull request Jul 17, 2025

Rollup of 15 pull requests #144071

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bors added the merged-by-bors This PR was explicitly merged by bors. label Jul 17, 2025

bors merged commit 9cd918b into rust-lang:master Jul 17, 2025
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rustbot added this to the 1.90.0 milestone Jul 17, 2025

oli-obk mentioned this pull request Jul 14, 2025

Tracking Issue for RFC 3762, "Make trait methods callable in const contexts" #143874

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Muscraft pushed a commit to Muscraft/rust that referenced this pull request Jul 21, 2025

Auto merge of rust-lang#143879 - fee1-dead-contrib:push-lrlpoouyqqry,…

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… r=fmease parse `const trait Trait` r? oli-obk or anyone from project-const-traits cc `@rust-lang/project-const-traits`

flip1995 pushed a commit to flip1995/rust that referenced this pull request Jul 25, 2025

Auto merge of rust-lang#143879 - fee1-dead-contrib:push-lrlpoouyqqry,…

11e3ae3

… r=fmease parse `const trait Trait` r? oli-obk or anyone from project-const-traits cc `@rust-lang/project-const-traits`

ytmimi mentioned this pull request Jul 31, 2025

Formatting vis const trait produces invalid code rust-lang/rustfmt#6619

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ytmimi reviewed Jul 31, 2025

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This was referenced Aug 5, 2025

Gate const trait syntax #144956

Merged

fix: Reject async assoc fns of const traits/impls in ast_passes #144907

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npmccallum mentioned this pull request Aug 9, 2025

Make trait methods callable in const contexts rust-lang/rfcs#3762

Open

dtolnay mentioned this pull request Aug 13, 2025

Parse const Trait syntax dtolnay/syn#1887

Open

		\|\| self.check_keyword(exp!(Const)) && (self.is_keyword_ahead(1, &[kw::Trait])
		\|\| self.is_keyword_ahead(1, &[kw::Unsafe]) && self.is_keyword_ahead(2, &[kw::Trait, kw::Auto]))

parse const trait Trait #143879

parse const trait Trait #143879

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Test differences

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parse `const trait Trait` #143879

parse `const trait Trait` #143879

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