Feature gate for defaulted associated type_consts with associated_type_defaults #152385

LaneAsade · 2026-02-09T13:14:18Z

This PR for issue #130288 extends a feature gate that was already present for defaulted associated types to defaulted type consts under associated_type_defaults.

Code added:

ast::AssocItemKind::Const(_) => {
                if let (AssocCtxt::Trait, true) =
                    (ctxt, i.attrs.iter().any(|attr| attr.has_name(sym::type_const)))
                {
                    gate!(
                        &self,
                        associated_type_defaults,
                        i.span,
                        "associated type defaults are unstable"
                    );
                }
                false
            }

Error produced:

error[E0658]: associated type defaults are unstable
 --> C:\Users\nigal\Downloads\rustIssue.rs:5:5
  |
5 |     const ASSOC:usize=10;
  |     ^^^^^^^^^^^^^^^^^^^^^
  |
  = note: see issue #29661 <https://github.com/rust-lang/rust/issues/29661> for more information
  = help: add `#![feature(associated_type_defaults)]` to the crate attributes to enable

warning: the feature `min_generic_const_args` is incomplete and may not be safe to use and/or cause compiler crashes
 --> C:\Users\nigal\Downloads\rustIssue.rs:1:12
  |
1 | #![feature(min_generic_const_args)]
  |            ^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: see issue #132980 <https://github.com/rust-lang/rust/issues/132980> for more information
  = note: `#[warn(incomplete_features)]` on by default

error: aborting due to 1 previous error; 1 warning emitted

For more information about this error, try `rustc --explain E0658`.

Thanks to @BoxyUwU for the guidance on this issue.

rustbot · 2026-02-09T13:14:24Z

r? @TaKO8Ki

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BoxyUwU · 2026-02-09T13:26:27Z

r? BoxyUwU

tests/ui/feature-gates/type-const-associated-default.rs

compiler/rustc_ast_passes/src/feature_gate.rs

tests/ui/feature-gates/type-const-associated-default.rs

Co-authored-by: Boxy <rust@boxyuwu.dev>

rustbot · 2026-02-10T16:39:35Z

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.

rustbot · 2026-02-10T16:39:35Z

⚠️ Warning ⚠️

The following commits have merge commits (commits with multiple parents) in your changes. We have a no merge policy so these commits will need to be removed for this pull request to be merged.
- a96fdd5
You can start a rebase with the following commands:
```
$ # rebase
$ git pull --rebase https://github.com/rust-lang/rust.git main
$ git push --force-with-lease
```

rust-log-analyzer · 2026-02-10T17:31:20Z

The job aarch64-gnu-llvm-20-1 failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

##[group]Runner Image Provisioner
Hosted Compute Agent
Version: 20260123.484
Commit: 6bd6555ca37d84114959e1c76d2c01448ff61c5d
Build Date: 2026-01-23T19:41:17Z
Worker ID: {f6da8854-ade4-4b3c-9b89-f2f3a4fa10dd}
Azure Region: southcentralus
##[endgroup]
##[group]VM Image
- OS: Linux (arm64)
- Source: Partner
- Name: Ubuntu 24.04 by Arm Limited
---
REPOSITORY                                   TAG       IMAGE ID       CREATED       SIZE
ghcr.io/dependabot/dependabot-updater-core   latest    afc745c7535d   2 weeks ago   783MB
=> Removing docker images...
Deleted Images:
untagged: ghcr.io/dependabot/dependabot-updater-core:latest
untagged: ghcr.io/dependabot/dependabot-updater-core@sha256:faae3d3a1dedd24cde388bb506bbacc0f7ed1eae99ebac129af66acd8540c84a
deleted: sha256:afc745c7535da1bb12f92c273b9a7e9c52c3f12c5873714b2542da259c6d9769
deleted: sha256:64e147d5e54d9be8b8aa322e511cda02296eda4b8b8d063c6a314833aca50e29
deleted: sha256:5cba409bb463f4e7fa1a19f695450170422582c1bc7c0e934d893b4e5f558bc6
deleted: sha256:cddc6ebd344b0111eaab170ead1dfda24acdfe865ed8a12599a34d338fa8e28b
deleted: sha256:2412c3f334d79134573cd45e657fb6cc0abd75bef3881458b0d498d936545c8d
---
test [ui] tests/ui/abi/abi-sysv64-register-usage.rs ... ignored, ignored when the architecture is aarch64
test [ui] tests/ui/abi/abi-typo-unstable.rs#feature_disabled ... ok
test [ui] tests/ui/abi/abi-typo-unstable.rs#feature_enabled ... ok
test [ui] tests/ui/abi/anon-extern-mod.rs ... ok
test [ui] tests/ui/abi/avr-sram.rs#disable_sram ... ok
test [ui] tests/ui/abi/avr-sram.rs#has_sram ... ok
test [ui] tests/ui/abi/arm-unadjusted-intrinsic.rs#aarch64 ... ok
test [ui] tests/ui/abi/avr-sram.rs#no_sram ... ok
test [ui] tests/ui/abi/arm-unadjusted-intrinsic.rs#arm ... ok
test [ui] tests/ui/abi/bad-custom.rs ... ok
test [ui] tests/ui/abi/c-stack-as-value.rs ... ok
test [ui] tests/ui/abi/c-zst.rs#aarch64-darwin ... ok
test [ui] tests/ui/abi/c-zst.rs#powerpc-linux ... ok
---
test [ui] tests/ui/asm/aarch64/ttbr0_el2.rs ... ok
test [ui] tests/ui/asm/aarch64/type-check-2.rs ... ok
test [ui] tests/ui/asm/aarch64/type-check-3.rs ... ok
test [ui] tests/ui/asm/aarch64/type-f16.rs ... ok
test [ui] tests/ui/asm/aarch64v8r.rs#r82 ... ok
test [ui] tests/ui/asm/aarch64v8r.rs#hf ... ok
test [ui] tests/ui/asm/aarch64/sym.rs ... ok
test [ui] tests/ui/asm/aarch64v8r.rs#sf ... ok
test [ui] tests/ui/asm/arm-low-dreg.rs ... ok
test [ui] tests/ui/asm/asm-with-nested-closure.rs ... ok
test [ui] tests/ui/asm/binary_asm_labels.rs ... ignored, only executed when the architecture is x86_64
test [ui] tests/ui/asm/cfg-parse-error.rs ... ok
test [ui] tests/ui/asm/cfg.rs#reva ... ignored, only executed when the architecture is x86_64
---
test [ui] tests/ui/const-generics/occurs-check/unused-substs-2.rs ... ok
test [ui] tests/ui/const-generics/occurs-check/unused-substs-3.rs ... ok
test [ui] tests/ui/const-generics/occurs-check/unused-substs-4.rs ... ok
test [ui] tests/ui/const-generics/occurs-check/unused-substs-5.rs ... ok
test [ui] tests/ui/const-generics/ogca/basic.rs ... ok
test [ui] tests/ui/const-generics/ogca/basic-fail.rs ... ok
test [ui] tests/ui/const-generics/ogca/coherence-ambiguous.rs ... ok
test [ui] tests/ui/const-generics/ogca/rhs-but-not-root.rs ... ok
test [ui] tests/ui/const-generics/opaque_types.rs ... ok
test [ui] tests/ui/const-generics/outer-lifetime-in-const-generic-default.rs ... ok
test [ui] tests/ui/const-generics/opaque_types2.rs ... ok
test [ui] tests/ui/const-generics/overlapping_impls.rs ... ok
test [ui] tests/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.rs#full ... ok
---
test [ui] tests/ui/extern/issue-64655-extern-rust-must-allow-unwind.rs#fat2 ... ok
test [ui] tests/ui/extern/issue-64655-extern-rust-must-allow-unwind.rs#fat3 ... ok
test [ui] tests/ui/extern/issue-80074.rs ... ok
test [ui] tests/ui/extern/issue-95829.rs ... ok
test [ui] tests/ui/extern/lgamma-linkage.rs ... ok
test [ui] tests/ui/extern/no-mangle-associated-fn.rs ... ok
test [ui] tests/ui/extern/not-in-block.rs ... ok
test [ui] tests/ui/extern/unsized-extern-derefmove.rs ... ok
test [ui] tests/ui/extern/windows-tcb-trash-13259.rs ... ok
test [ui] tests/ui/feature-gates/allow-features-empty.rs ... ok
---
test [ui] tests/ui/feature-gates/feature-gate-macro-derive.rs ... ok
test [ui] tests/ui/feature-gates/feature-gate-macro-metavar-expr-concat.rs ... ok
test [ui] tests/ui/feature-gates/feature-gate-marker_trait_attr.rs ... ok
test [ui] tests/ui/feature-gates/feature-gate-may-dangle.rs ... ok
test [ui] tests/ui/feature-gates/feature-gate-mgca-type-const-syntax.rs ... ok
test [ui] tests/ui/feature-gates/feature-gate-min-generic-const-args.rs ... ok
test [ui] tests/ui/feature-gates/feature-gate-movrs_target_feature.rs ... ignored, only executed when the architecture is x86_64
test [ui] tests/ui/feature-gates/feature-gate-more-maybe-bounds.rs ... ok
test [ui] tests/ui/feature-gates/feature-gate-min_const_fn.rs ... ok
test [ui] tests/ui/feature-gates/feature-gate-naked_functions_rustic_abi.rs ... ignored, only executed when the architecture is x86_64
---
test [ui] tests/ui/imports/ambiguous-7.rs ... ok
test [ui] tests/ui/imports/ambiguous-import-visibility-module.rs ... ok
test [ui] tests/ui/imports/ambiguous-8.rs ... ok
test [ui] tests/ui/imports/ambiguous-glob-vs-expanded-extern.rs ... ok
test [ui] tests/ui/imports/ambiguous-panic-glob-vs-multiouter.rs ... ok
test [ui] tests/ui/imports/ambiguous-panic-globvsglob.rs ... ok
test [ui] tests/ui/imports/ambiguous-panic-no-implicit-prelude.rs ... ok
test [ui] tests/ui/imports/ambiguous-panic-non-prelude-core-glob.rs ... ok
test [ui] tests/ui/imports/ambiguous-panic-non-prelude-std-glob.rs ... ok
test [ui] tests/ui/imports/ambiguous-panic-pick-core.rs ... ok
test [ui] tests/ui/imports/ambiguous-panic-pick-std.rs ... ok
---
- LL |     const N: usize = 10;
-    |     ^^^^^^^^^^^^^^^^^^^^
-    |
-    = note: see issue #29661 <https://github.com/rust-lang/rust/issues/29661> for more information
-    = help: add `#![feature(associated_type_defaults)]` to the crate attributes to enable
-    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+ LL |     #[type_const]
+    |       ^^^^^^^^^^
10 
11 warning: the feature `min_generic_const_args` is incomplete and may not be safe to use and/or cause compiler crashes
-   --> $DIR/type-const-associated-default.rs:2:12
+   --> $DIR/type-const-associated-default.rs:1:12
---
To only update this specific test, also pass `--test-args const-generics/mgca/type-const-associated-default.rs`

error: 1 errors occurred comparing output.
status: exit status: 1
command: env -u RUSTC_LOG_COLOR RUSTC_ICE="0" RUST_BACKTRACE="short" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/tests/ui/const-generics/mgca/type-const-associated-default.rs" "-Zthreads=1" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "-Z" "ignore-directory-in-diagnostics-source-blocks=/cargo" "-Z" "ignore-directory-in-diagnostics-source-blocks=/checkout/vendor" "--sysroot" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2" "--target=aarch64-unknown-linux-gnu" "--check-cfg" "cfg(test,FALSE)" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Zwrite-long-types-to-disk=no" "-Cstrip=debuginfo" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/aarch64-unknown-linux-gnu/test/ui/const-generics/mgca/type-const-associated-default" "-A" "unused" "-W" "unused_attributes" "-A" "internal_features" "-A" "unused_parens" "-A" "unused_braces" "-Crpath" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/aarch64-unknown-linux-gnu/native/rust-test-helpers"
stdout: none
--- stderr -------------------------------
error: cannot find attribute `type_const` in this scope
##[error]  --> /checkout/tests/ui/const-generics/mgca/type-const-associated-default.rs:4:7
   |

gate defaulted type consts with associated_type_defaults

5592c3a

rustbot assigned TaKO8Ki Feb 9, 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 Feb 9, 2026

LaneAsade changed the title ~~Feature gate for defaulted associated type_consts with associated_type_defaults #130288~~ Feature gate for defaulted associated type_consts with associated_type_defaults Feb 9, 2026

Fix formatting in type-const-associated-default.rs

e47237c

rustbot assigned BoxyUwU and unassigned TaKO8Ki Feb 9, 2026

Fix formatting in type-const-associated-default.rs

6385c39

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compiler/rustc_ast_passes/src/feature_gate.rs Outdated Show resolved Hide resolved

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LaneAsade and others added 2 commits February 10, 2026 22:06

Update tests/ui/feature-gates/type-const-associated-default.rs

dac6b9b

Co-authored-by: Boxy <rust@boxyuwu.dev>

Merge branch 'main' into gate-type-const-defaults

a96fdd5

rustbot added has-merge-commits PR has merge commits, merge with caution. S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Feb 10, 2026

Move type-const-default-associated-type UI test to const-generics/mgca

1867a9d

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Feature gate for defaulted associated type_consts with associated_type_defaults #152385

Feature gate for defaulted associated type_consts with associated_type_defaults #152385

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