Implement unstable trait impl #140399

tiif · 2025-04-28T15:13:52Z

This PR allows marking impls of stable trait with stable type as unstable.

The design and mentoring are done by @BoxyUwU

tests/ui/internal/unstable-impl-assoc-type.rs

bors · 2025-06-10T21:33:29Z

☔ The latest upstream changes (presumably #142299) made this pull request unmergeable. Please resolve the merge conflicts.

tiif · 2025-06-11T15:49:23Z

tests/ui/internal/unstable_impl_codegen.rs

If we stop making TypingMode::PostAnalysis return Ok(Yes) when proving ClauseKind::UnstableFeature, this test will ice: #142368 (comment)

This means the test is working as intended,

jhpratt · 2025-06-11T23:58:24Z

I've got nothing technical to add (I've not looked over the code). I just wanted to thank @tiif for taking on this task! It's far from trivial and has been a long-standing desire.

bors · 2025-06-14T08:38:10Z

☔ The latest upstream changes (presumably #142483) made this pull request unmergeable. Please resolve the merge conflicts.

BoxyUwU

gg gamer

compiler/rustc_hir_analysis/src/check/wfcheck.rs

compiler/rustc_attr_data_structures/src/attributes.rs

compiler/rustc_attr_parsing/src/attributes/allow_unstable.rs

compiler/rustc_hir_analysis/src/collect/predicates_of.rs

compiler/rustc_passes/src/stability.rs

compiler/rustc_type_ir/src/flags.rs

compiler/rustc_feature/src/unstable.rs

compiler/rustc_next_trait_solver/src/solve/mod.rs

compiler/rustc_middle/src/ty/context.rs

compiler/rustc_passes/src/check_attr.rs

compiler/rustc_trait_selection/src/traits/fulfill.rs

tests/ui/internal/unstable_feature_bound_staged_api.rs

tiif · 2025-06-23T13:49:07Z

I am leaving the conflicts there because I don't want to rebase for now (the conflict also happens quite frequently), so it would be easier for boxy to review.

hi @jdonszelmann, it'd be nice to get a vibeck from you for the attribute change :)

rustbot · 2025-06-23T13:50:19Z

Some changes occurred in compiler/rustc_attr_parsing

cc @jdonszelmann

changes to the core type system

cc @compiler-errors, @lcnr

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

cc @jdonszelmann

changes to inspect_obligations.rs

cc @compiler-errors, @lcnr

Some changes occurred in compiler/rustc_attr_data_structures

cc @jdonszelmann

jdonszelmann · 2025-06-23T13:51:52Z

Hi tiff! Will review this week :)

bors · 2025-06-25T07:50:50Z

☔ The latest upstream changes (presumably #142997) made this pull request unmergeable. Please resolve the merge conflicts.

jdonszelmann

looks good from my side tiff!

jdonszelmann · 2025-06-27T09:42:32Z

compiler/rustc_attr_data_structures/src/attributes.rs

@@ -268,5 +268,7 @@ pub enum AttributeKind {
        /// Span of the attribute.
        span: Span,
    },
+    /// Represents `#[unstable_feature_bound]`.


add a space above this simply to be consistent with the other ones (minor hehe)

jdonszelmann · 2025-06-27T09:45:08Z

compiler/rustc_feature/src/builtin_attrs.rs

@@ -675,6 +675,10 @@ pub static BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
        template!(List: r#"feature = "name", reason = "...", issue = "N""#), DuplicatesOk,
        EncodeCrossCrate::Yes
    ),
+    ungated!(
+        unstable_feature_bound, Normal, template!(Word, List: "feat1, feat2, ..."),
+        DuplicatesOk, EncodeCrossCrate::No,


we're moving lots of this info into the attribute system, that's why it duplicates the template for now. When you'll rebase on master you'll also have to duplicate the cross-crate-encoding somewhere else to make it compile

…in effect

bors · 2025-06-27T19:58:56Z

☔ The latest upstream changes (presumably #143091) made this pull request unmergeable. Please resolve the merge conflicts.

rust-cloud-vms bot force-pushed the unstable_impl branch from d01f12a to 9e139e1 Compare May 23, 2025 10:26

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BoxyUwU self-assigned this May 27, 2025

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rust-cloud-vms bot force-pushed the unstable_impl branch from 486d3d3 to 02f780f Compare May 30, 2025 09:52

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BoxyUwU mentioned this pull request Jun 2, 2025

Impl stability is not checked #55436

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rust-cloud-vms bot force-pushed the unstable_impl branch from 567ec89 to 80fd239 Compare June 9, 2025 09:06

BoxyUwU reviewed Jun 10, 2025

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rust-cloud-vms bot force-pushed the unstable_impl branch from 850e3e1 to 27d9e21 Compare June 11, 2025 13:39

tiif mentioned this pull request Jun 11, 2025

Try: stop special casing codegen for unstable impl #142368

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rust-cloud-vms bot force-pushed the unstable_impl branch from a77d746 to 6e4c902 Compare June 13, 2025 16:09

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BoxyUwU reviewed Jun 17, 2025

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tiif commented Jun 20, 2025

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tiif changed the title ~~WIP: Unstable impls~~ Implement unstable trait impl Jun 21, 2025

tiif marked this pull request as ready for review June 23, 2025 13:50

rust-cloud-vms bot force-pushed the unstable_impl branch from 5529925 to 5e2dc7b Compare June 24, 2025 15:56

jdonszelmann reviewed Jun 27, 2025

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rust-cloud-vms bot force-pushed the unstable_impl branch from 4add001 to fd34b00 Compare June 27, 2025 15:18

tiif added 7 commits June 27, 2025 15:45

Setup unstable feature bound attribute

7ac74c5

Lower the unstable feature bound attribute to UnstableFeature predicate

0751165

Add the core logic in both old solver and new solver

0d5693b

Implement other logics

98216fb

Make stability attribute not to error when unstable feature bound is …

39c5866

…in effect

Add tests

373f6dd

Fix rebase error

a90c483

rust-cloud-vms bot force-pushed the unstable_impl branch from fd34b00 to a90c483 Compare June 27, 2025 15:58

Implement unstable trait impl #140399

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Implement unstable trait impl #140399

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tiif commented Apr 28, 2025 •

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