mgca: Lower all const paths as `ConstArgKind::Path` #135186

camelid · 2025-01-07T05:21:38Z

When #![feature(min_generic_const_args)] is enabled, we now lower all
const paths in generic arg position to hir::ConstArgKind::Path. We
then lower assoc const paths to ty::ConstKind::Unevaluated since we
can no longer use the anon const expression lowering machinery. In the
process of implementing this, I factored out hir_ty_lowering code that
is now shared between lowering assoc types and assoc consts.

This PR also introduces a #[type_const] attribute for trait assoc
consts that are allowed as const args. However, we still need to
implement code to check that assoc const definitions satisfy
#[type_const] if present (basically is it a const path or a
monomorphic anon const).

r? @BoxyUwU

rustbot · 2025-01-11T02:51:48Z

Some changes occurred in const_evaluatable.rs

cc @BoxyUwU

HIR ty lowering was modified

cc @fmease

BoxyUwU

thx for working on this :3

compiler/rustc_ast_lowering/src/lib.rs

compiler/rustc_ast/src/ast.rs

compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs

compiler/rustc_hir_analysis/src/collect.rs

bors · 2025-01-23T01:51:57Z

☔ The latest upstream changes (presumably #135896) made this pull request unmergeable. Please resolve the merge conflicts.

bors · 2025-01-27T15:23:39Z

☔ The latest upstream changes (presumably #136024) made this pull request unmergeable. Please resolve the merge conflicts.

compiler/rustc_ast/src/util/const_args.rs

compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs

bors · 2025-02-25T03:00:32Z

☔ The latest upstream changes (presumably #135726) made this pull request unmergeable. Please resolve the merge conflicts.

A bit tricky to support this special case now, so might as well save it for once we're ready to handle the general case. See rust-lang#135186 (comment). Co-authored-by: BoxyUwU <rust@boxyuwu.dev>

BoxyUwU · 2025-03-04T04:58:37Z

lgtm, once you've squashed the commits ill r+ (and probably should update the PR description/title)

When `#![feature(min_generic_const_args)]` is enabled, we now lower all const paths in generic arg position to `hir::ConstArgKind::Path`. We then lower assoc const paths to `ty::ConstKind::Unevaluated` since we can no longer use the anon const expression lowering machinery. In the process of implementing this, I factored out `hir_ty_lowering` code that is now shared between lowering assoc types and assoc consts. This PR also introduces a `#[type_const]` attribute for trait assoc consts that are allowed as const args. However, we still need to implement code to check that assoc const definitions satisfy `#[type_const]` if present (basically is it a const path or a monomorphic anon const).

BoxyUwU · 2025-03-04T17:37:57Z

@bors r+ rollup=never

bors · 2025-03-04T17:37:59Z

📌 Commit 177e7ff has been approved by BoxyUwU

It is now in the queue for this repository.

bors · 2025-03-04T22:37:40Z

⌛ Testing commit 177e7ff with merge 08db600...

bors · 2025-03-05T01:53:44Z

☀️ Test successful - checks-actions
Approved by: BoxyUwU
Pushing 08db600 to master...

rust-timer · 2025-03-05T03:11:05Z

Finished benchmarking commit (08db600): comparison URL.

Overall result: ❌ regressions - no action needed

@rustbot label: -perf-regression

Instruction count

This is the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.3%	[0.3%, 0.3%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (secondary 0.6%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	2.1%	[1.8%, 2.4%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.3%	[-2.3%, -2.3%]	1
All ❌✅ (primary)	-	-	0

Cycles

Results (secondary -2.1%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.1%	[-2.1%, -2.1%]	1
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 778.226s -> 775.839s (-0.31%)
Artifact size: 362.05 MiB -> 362.04 MiB (-0.00%)

rustbot assigned BoxyUwU Jan 7, 2025

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camelid changed the title ~~Start lowering multi-segment const paths as ConstArgKind::Path~~ Lower multi-segment const paths as ConstArgKind::Path Jan 7, 2025

camelid force-pushed the const-path-multi branch from c501669 to 4efbed3 Compare January 7, 2025 18:52

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camelid force-pushed the const-path-multi branch from 4efbed3 to 0036c2c Compare January 7, 2025 19:13

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camelid marked this pull request as ready for review January 11, 2025 02:51

camelid changed the title ~~Lower multi-segment const paths as ConstArgKind::Path~~ Lower multi-segment const paths as ConstArgKind::Path Jan 11, 2025

BoxyUwU reviewed Jan 16, 2025

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camelid force-pushed the const-path-multi branch from 263637d to a296ff8 Compare January 20, 2025 04:47

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camelid force-pushed the const-path-multi branch from a5a9370 to ece9e77 Compare January 23, 2025 06:13

BoxyUwU 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 Jan 23, 2025

camelid 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 Jan 27, 2025

camelid changed the title ~~Lower multi-segment const paths as ConstArgKind::Path~~ Lower all trivial const paths as ConstArgKind::Path Jan 27, 2025

BoxyUwU reviewed Jan 28, 2025

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compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs Show resolved Hide resolved

BoxyUwU 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 Jan 28, 2025

camelid force-pushed the const-path-multi branch from 7cbecce to 50bd398 Compare February 3, 2025 05:34

camelid force-pushed the const-path-multi branch from abe7d68 to 991f55c Compare March 4, 2025 03:59

camelid 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 Mar 4, 2025

BoxyUwU 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 Mar 4, 2025

camelid changed the title ~~Lower all trivial const paths as ConstArgKind::Path~~ mgca: Lower all const paths as ConstArgKind::Path Mar 4, 2025

camelid force-pushed the const-path-multi branch from c082ce1 to 177e7ff Compare March 4, 2025 15:11

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-review Status: Awaiting review from the assignee but also interested parties. labels Mar 4, 2025

bors added the merged-by-bors This PR was explicitly merged by bors. label Mar 5, 2025

bors merged commit 08db600 into rust-lang:master Mar 5, 2025
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rustbot added this to the 1.87.0 milestone Mar 5, 2025

camelid deleted the const-path-multi branch March 5, 2025 02:31

matthiaskrgr mentioned this pull request Mar 6, 2025

ICE: assertion failed: !parent_args.is_empty() #138088

Open

BoxyUwU mentioned this pull request Mar 12, 2025

Tracking Issue for Generic Constant Arguments MVP #132980

Open

15 tasks

This was referenced Apr 2, 2025

ICE: DefId::expect_local DefId isn't local #133808

Open

ICE: Instance::try_resolve should only be used to resolve instances of functions, statics, and consts; to resolve associated types, use try_normalize_erasing_regions #139596

Open

mgca: Lower all const paths as ConstArgKind::Path #135186

mgca: Lower all const paths as ConstArgKind::Path #135186

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rust-timer commented Mar 5, 2025

Overall result: ❌ regressions - no action needed

Instruction count

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Cycles

Binary size

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mgca: Lower all const paths as `ConstArgKind::Path` #135186

mgca: Lower all const paths as `ConstArgKind::Path` #135186

camelid commented Jan 7, 2025 •

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