implement #![feature(macroless_generic_const_args)] by khyperia · Pull Request #159058 · rust-lang/rust

khyperia · 2026-07-10T06:55:45Z

tracking issue: #159006

lots of description of what is happening here in the tracking issue, not gonna copypaste it into here :)

the test situation is that after discussion with boxy of whether our mgca tests should be:

keep them under only min_generic_const_args, and add direct_const_arg!() where it's needed
keep the code contents as-is, and add #![feature(macroless_generic_const_args)] where it's needed

the second seems more desirable, so that's what I did. There are still quite a few tests that only have min_generic_const_args without macroless_generic_const_args (140 of them, to be exact - rg --files-without-match macroless_generic_const_args $(rg -g '*.rs' --files-with-matches min_generic_const_args tests) | wc -l, and now 90 with macroless_generic_const_args)

r? @BoxyUwU

rustbot · 2026-07-10T06:55:48Z

Some changes occurred in tests/ui/sanitizer

cc @rcvalle

HIR ty lowering was modified

cc @fmease

rustbot · 2026-07-10T06:55:51Z

BoxyUwU is currently at their maximum review capacity.
They may take a while to respond.

khyperia · 2026-07-10T06:59:07Z

            ConstItemRhsKind::TypeConst { rhs: Some(anon) } => {
-                hir::ConstItemRhs::TypeConst(self.lower_anon_const_to_const_arg_and_alloc(anon))
+                hir::ConstItemRhs::TypeConst(self.arena.alloc(
+                    match self.can_lower_expr_to_const_arg_direct(
+                        &anon.value,
+                        DirectConstArgContext::MacrolessMinGenericConstArgs,
+                    ) {
+                        Ok(()) => self.lower_expr_to_const_arg_direct(&anon.value, Some(anon.id)),
+                        Err(err) => err.emit(self),
+                    },
+                ))
            }


ConstItemRhsKind::TypeConst no longer needs to contain an AnonConst, it can parse identically to the rhs of a regular const, as a normal expr now.

Doing so I've left undone for now, will do so in a followup, it gets a bit more involved (and it's related to this #158617 (comment) that I might do at the same time)

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rustbot · 2026-07-10T10:06:50Z

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.

kn1g78 · 2026-07-10T14:13:05Z

+}
+```
+
+Using `#![macroless_generic_const_args]` enables you to write the above without the macro:


I think this should be #![feature(macroless_generic_const_args)], as shown in the example below.

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rustbot · 2026-07-18T08:17:05Z

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.

BoxyUwU

what's the behaviour of direct!(Foo { field: T::ASSOC })? Because I dont think we wan't to accept such a thing, instead field: direct!(T::ASSOC) should be required. Ideally macroful gca should not expose macroless gca's heuristic to any extent because then it needs to be figured out for stabilization 🤔

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BoxyUwU · 2026-07-21T09:54:49Z

@bors r+

thx :3

rust-bors · 2026-07-21T09:54:52Z

📌 Commit a388f03 has been approved by BoxyUwU

It is now in the queue for this repository.

…uwer Rollup of 7 pull requests Successful merges: - #155617 (Replace `jemalloc` bootstrap options with `override-allocator`) - #156225 (feat(num): improve error messages for `TryFromIntError`) - #159058 (implement #![feature(macroless_generic_const_args)]) - #159435 (core: implement `Rng` for references) - #159471 (Make `Global` and `System` allocators unstably implement `const Clone + const Default`.) - #159590 (Remove some dead code) - #159636 (Improve some comments (and an error message))

@BoxyUwU

Rollup merge of #159058 - khyperia:macroless_generic_const_args, r=BoxyUwU implement #![feature(macroless_generic_const_args)] tracking issue: #159006 lots of description of what is happening here in the tracking issue, not gonna copypaste it into here :) the test situation is that after discussion with boxy of whether our mgca tests should be: - keep them under only `min_generic_const_args`, and add `direct_const_arg!()` where it's needed - keep the code contents as-is, and add `#![feature(macroless_generic_const_args)]` where it's needed the second seems more desirable, so that's what I did. There are still quite a few tests that only have `min_generic_const_args` without `macroless_generic_const_args` (140 of them, to be exact - `rg --files-without-match macroless_generic_const_args $(rg -g '*.rs' --files-with-matches min_generic_const_args tests) | wc -l`, and now 90 with `macroless_generic_const_args`) r? @BoxyUwU

…uwer Rollup of 7 pull requests Successful merges: - rust-lang/rust#155617 (Replace `jemalloc` bootstrap options with `override-allocator`) - rust-lang/rust#156225 (feat(num): improve error messages for `TryFromIntError`) - rust-lang/rust#159058 (implement #![feature(macroless_generic_const_args)]) - rust-lang/rust#159435 (core: implement `Rng` for references) - rust-lang/rust#159471 (Make `Global` and `System` allocators unstably implement `const Clone + const Default`.) - rust-lang/rust#159590 (Remove some dead code) - rust-lang/rust#159636 (Improve some comments (and an error message))

@BoxyUwU

…wU,bit-aloo clean up handling of paths in mgca related tracking issue: rust-lang#132980 Handling of ambiguous type-or-constant argument paths was really wonky and distinct from the regular `can_lower_expr_to_const_arg_direct` lowering paths. Clean that up and unify it, as discussed here rust-lang#158479 (comment) Also, do a bunch of other little cleanups at the same time while I'm here: - add support for parens to the inside of direct_const_arg! and macroless_generic_const_args (idk why this wasn't a thing before) - add constant and lifetime ribs when resolving TyKind::DirectConstArg - note the TyKind, not ExprKind (~~I am unsure if/how this changes behavior~~ added a test, `direct-const-arg-correct-rib.rs`) - this was discussed here rust-lang#158617 (comment) - minor debug logging change - various minor code shuffles/cleanups - add test for `direct_const_arg!(_)` inferring to a type - this test should have been added in rust-lang#159058 which added this behavior (well, changed the behavior from an ICE to inferring to a type) - add a test asserting the current behavior of parens/braces/underscores on stable - one or two of these cases already have tests elsewhere, but it's nice to assert the whole set, and also assert the whole set in the same place so it's easily visible to be able to give me confidence the whole set actually is tested (both positives and negatives are important here) - add a test similar to the previous one, but with mgca enabled, asserting all combinations now compile successfully r? @BoxyUwU

@BoxyUwU

Rollup merge of #160216 - khyperia:gca-path-cleanup, r=BoxyUwU,bit-aloo clean up handling of paths in mgca related tracking issue: #132980 Handling of ambiguous type-or-constant argument paths was really wonky and distinct from the regular `can_lower_expr_to_const_arg_direct` lowering paths. Clean that up and unify it, as discussed here #158479 (comment) Also, do a bunch of other little cleanups at the same time while I'm here: - add support for parens to the inside of direct_const_arg! and macroless_generic_const_args (idk why this wasn't a thing before) - add constant and lifetime ribs when resolving TyKind::DirectConstArg - note the TyKind, not ExprKind (~~I am unsure if/how this changes behavior~~ added a test, `direct-const-arg-correct-rib.rs`) - this was discussed here #158617 (comment) - minor debug logging change - various minor code shuffles/cleanups - add test for `direct_const_arg!(_)` inferring to a type - this test should have been added in #159058 which added this behavior (well, changed the behavior from an ICE to inferring to a type) - add a test asserting the current behavior of parens/braces/underscores on stable - one or two of these cases already have tests elsewhere, but it's nice to assert the whole set, and also assert the whole set in the same place so it's easily visible to be able to give me confidence the whole set actually is tested (both positives and negatives are important here) - add a test similar to the previous one, but with mgca enabled, asserting all combinations now compile successfully r? @BoxyUwU

rustbot added PG-exploit-mitigations Project group: Exploit mitigations 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 Jul 10, 2026

rustbot assigned BoxyUwU Jul 10, 2026

khyperia mentioned this pull request Jul 10, 2026

Tracking Issue for macroless_generic_const_args #159006

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khyperia force-pushed the macroless_generic_const_args branch from 925742b to 4e77ce1 Compare July 10, 2026 10:06

rustbot added the T-rustdoc-frontend Relevant to the rustdoc-frontend team, which will review and decide on the web UI/UX output. label Jul 10, 2026

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khyperia force-pushed the macroless_generic_const_args branch from 4e77ce1 to 6862ede Compare July 18, 2026 08:17

khyperia mentioned this pull request Jul 20, 2026

unify the AST repr of type const and const RHS #159596

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macroless_generic_const_args

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khyperia force-pushed the macroless_generic_const_args branch from 6862ede to a388f03 Compare July 20, 2026 16:25

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 Jul 21, 2026

JonathanBrouwer mentioned this pull request Jul 21, 2026

Rollup of 7 pull requests #159650

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BoxyUwU mentioned this pull request Jul 21, 2026

Full Const Generics rust-lang/goals#100

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rust-bors Bot merged commit fd4b1d5 into rust-lang:main Jul 21, 2026
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khyperia deleted the macroless_generic_const_args branch July 22, 2026 07:14

khyperia mentioned this pull request Jul 30, 2026

clean up handling of paths in mgca #160216

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implement #![feature(macroless_generic_const_args)] - #159058

implement #![feature(macroless_generic_const_args)]#159058
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