…=fee1-dead

New const traits syntax

This PR only affects the AST and doesn't actually change anything semantically.

All occurrences of `~const` outside of libcore have been replaced by `[const]`. Within libcore we have to wait for rustfmt to be bumped in the bootstrap compiler. This will happen "automatically" (when rustfmt is run) during the bootstrap bump, as rustfmt converts `~const` into `[const]`. After this we can remove the `~const` support from the parser

Caveat discovered during impl: there is no legacy bare trait object recovery for `[const] Trait` as that snippet in type position goes down the slice /array parsing code and will error

r? `@fee1-dead`

cc `@nikomatsakis` `@traviscross` `@compiler-errors`

…rors

Rollup of 8 pull requests

Successful merges:

 - #139858 (New const traits syntax)
 - #140809 (Reduce special casing for the panic runtime)
 - #142963 (Skip unnecessary components in x64 try builds)
 - #142974 (Update stage0 to 1.89.0-beta.1)
 - #142987 (rustdoc: show attributes on enum variants)
 - #143002 (tests: Require `run-fail` ui tests to have an exit code (`SIGABRT` not ok))
 - #143092 (const checks for lifetime-extended temporaries: avoid 'top-level scope' terminology)
 - #143096 (tag_for_variant: properly pass TypingEnv)

r? `@ghost`
`@rustbot` modify labels: rollup

Rollup of 9 pull requests

Successful merges:

 - #139858 (New const traits syntax)
 - #140809 (Reduce special casing for the panic runtime)
 - #142730 (suggest declaring modules when file found but module not defined)
 - #142806 (Normalize before computing ConstArgHasType goal in new solver)
 - #143046 (const validation: properly ignore zero-sized UnsafeCell)
 - #143092 (const checks for lifetime-extended temporaries: avoid 'top-level scope' terminology)
 - #143096 (tag_for_variant: properly pass TypingEnv)
 - #143104 (hir_analysis: prohibit `dyn PointeeSized`)
 - #143106 (gce: don't ICE on non-local const)

Failed merges:

 - #143036 (Remove support for `dyn*` from the compiler)

r? `@ghost`
`@rustbot` modify labels: rollup

Rollup merge of #139858 - oli-obk:new-const-traits-syntax, r=fee1-dead

New const traits syntax

This PR only affects the AST and doesn't actually change anything semantically.

All occurrences of `~const` outside of libcore have been replaced by `[const]`. Within libcore we have to wait for rustfmt to be bumped in the bootstrap compiler. This will happen "automatically" (when rustfmt is run) during the bootstrap bump, as rustfmt converts `~const` into `[const]`. After this we can remove the `~const` support from the parser

Caveat discovered during impl: there is no legacy bare trait object recovery for `[const] Trait` as that snippet in type position goes down the slice /array parsing code and will error

r? ``@fee1-dead``

cc ``@nikomatsakis`` ``@traviscross`` ``@compiler-errors``

Rollup of 9 pull requests

Successful merges:

 - rust-lang/rust#139858 (New const traits syntax)
 - rust-lang/rust#140809 (Reduce special casing for the panic runtime)
 - rust-lang/rust#142730 (suggest declaring modules when file found but module not defined)
 - rust-lang/rust#142806 (Normalize before computing ConstArgHasType goal in new solver)
 - rust-lang/rust#143046 (const validation: properly ignore zero-sized UnsafeCell)
 - rust-lang/rust#143092 (const checks for lifetime-extended temporaries: avoid 'top-level scope' terminology)
 - rust-lang/rust#143096 (tag_for_variant: properly pass TypingEnv)
 - rust-lang/rust#143104 (hir_analysis: prohibit `dyn PointeeSized`)
 - rust-lang/rust#143106 (gce: don't ICE on non-local const)

Failed merges:

 - rust-lang/rust#143036 (Remove support for `dyn*` from the compiler)

r? `@ghost`
`@rustbot` modify labels: rollup

Rollup of 9 pull requests

Successful merges:

 - rust-lang/rust#139858 (New const traits syntax)
 - rust-lang/rust#140809 (Reduce special casing for the panic runtime)
 - rust-lang/rust#142730 (suggest declaring modules when file found but module not defined)
 - rust-lang/rust#142806 (Normalize before computing ConstArgHasType goal in new solver)
 - rust-lang/rust#143046 (const validation: properly ignore zero-sized UnsafeCell)
 - rust-lang/rust#143092 (const checks for lifetime-extended temporaries: avoid 'top-level scope' terminology)
 - rust-lang/rust#143096 (tag_for_variant: properly pass TypingEnv)
 - rust-lang/rust#143104 (hir_analysis: prohibit `dyn PointeeSized`)
 - rust-lang/rust#143106 (gce: don't ICE on non-local const)

Failed merges:

 - rust-lang/rust#143036 (Remove support for `dyn*` from the compiler)

r? `@ghost`
`@rustbot` modify labels: rollup

…=fee1-dead

New const traits syntax

This PR only affects the AST and doesn't actually change anything semantically.

All occurrences of `~const` outside of libcore have been replaced by `[const]`. Within libcore we have to wait for rustfmt to be bumped in the bootstrap compiler. This will happen "automatically" (when rustfmt is run) during the bootstrap bump, as rustfmt converts `~const` into `[const]`. After this we can remove the `~const` support from the parser

Caveat discovered during impl: there is no legacy bare trait object recovery for `[const] Trait` as that snippet in type position goes down the slice /array parsing code and will error

r? ``@fee1-dead``

cc ``@nikomatsakis`` ``@traviscross`` ``@compiler-errors``

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [syn](https://redirect.github.com/dtolnay/syn) |
workspace.dependencies | patch | `2.0.104` -> `2.0.106` |

---

> [!WARNING]
> Some dependencies could not be looked up. Check the Dependency
Dashboard for more information.

---

### Release Notes

<details>
<summary>dtolnay/syn (syn)</summary>

###
[`v2.0.106`](https://redirect.github.com/dtolnay/syn/releases/tag/2.0.106)

[Compare
Source](https://redirect.github.com/dtolnay/syn/compare/2.0.105...2.0.106)

- Replace `~const` syntax with `[const]` conditionally const syntax in
trait bounds
([#&#8203;1896](https://redirect.github.com/dtolnay/syn/issues/1896),
[rust-lang/rust#139858](https://redirect.github.com/rust-lang/rust/pull/139858))
- Support conditionally const impl Trait types
([#&#8203;1897](https://redirect.github.com/dtolnay/syn/issues/1897))
- Reject polarity modifier and lifetime binder used in the same trait
bound
([#&#8203;1899](https://redirect.github.com/dtolnay/syn/issues/1899),
[rust-lang/rust#127054](https://redirect.github.com/rust-lang/rust/pull/127054))
- Parse const trait bounds with bound lifetimes
([#&#8203;1902](https://redirect.github.com/dtolnay/syn/issues/1902))
- Parse bound lifetimes with lifetime bounds
([#&#8203;1903](https://redirect.github.com/dtolnay/syn/issues/1903))
- Allow type parameters and const parameters in trait bounds and generic
closures
([#&#8203;1904](https://redirect.github.com/dtolnay/syn/issues/1904),
[#&#8203;1907](https://redirect.github.com/dtolnay/syn/issues/1907),
[#&#8203;1908](https://redirect.github.com/dtolnay/syn/issues/1908),
[#&#8203;1909](https://redirect.github.com/dtolnay/syn/issues/1909))

###
[`v2.0.105`](https://redirect.github.com/dtolnay/syn/releases/tag/2.0.105)

[Compare
Source](https://redirect.github.com/dtolnay/syn/compare/2.0.104...2.0.105)

- Disallow "negative" inherent impls like `impl !T {}`
([#&#8203;1881](https://redirect.github.com/dtolnay/syn/issues/1881),
[rust-lang/rust#144386](https://redirect.github.com/rust-lang/rust/pull/144386))

</details>

---

### Configuration

📅 **Schedule**: Branch creation - "before 4am on Monday" (UTC),
Automerge - At any time (no schedule defined).

🚦 **Automerge**: Disabled by config. Please merge this manually once you
are satisfied.

♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the
rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about this update
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---

- [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check
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---

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View the [repository job
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<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiI0MS44Mi43IiwidXBkYXRlZEluVmVyIjoiNDEuODIuNyIsInRhcmdldEJyYW5jaCI6Im1haW4iLCJsYWJlbHMiOlsiaW50ZXJuYWwiXX0=-->

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [syn](https://redirect.github.com/dtolnay/syn) |
workspace.dependencies | patch | `2.0.104` -> `2.0.106` |

---

> [!WARNING]
> Some dependencies could not be looked up. Check the Dependency
Dashboard for more information.

---

### Release Notes

<details>
<summary>dtolnay/syn (syn)</summary>

###
[`v2.0.106`](https://redirect.github.com/dtolnay/syn/releases/tag/2.0.106)

[Compare
Source](https://redirect.github.com/dtolnay/syn/compare/2.0.105...2.0.106)

- Replace `~const` syntax with `[const]` conditionally const syntax in
trait bounds
([#&#8203;1896](https://redirect.github.com/dtolnay/syn/issues/1896),
[rust-lang/rust#139858](https://redirect.github.com/rust-lang/rust/pull/139858))
- Support conditionally const impl Trait types
([#&#8203;1897](https://redirect.github.com/dtolnay/syn/issues/1897))
- Reject polarity modifier and lifetime binder used in the same trait
bound
([#&#8203;1899](https://redirect.github.com/dtolnay/syn/issues/1899),
[rust-lang/rust#127054](https://redirect.github.com/rust-lang/rust/pull/127054))
- Parse const trait bounds with bound lifetimes
([#&#8203;1902](https://redirect.github.com/dtolnay/syn/issues/1902))
- Parse bound lifetimes with lifetime bounds
([#&#8203;1903](https://redirect.github.com/dtolnay/syn/issues/1903))
- Allow type parameters and const parameters in trait bounds and generic
closures
([#&#8203;1904](https://redirect.github.com/dtolnay/syn/issues/1904),
[#&#8203;1907](https://redirect.github.com/dtolnay/syn/issues/1907),
[#&#8203;1908](https://redirect.github.com/dtolnay/syn/issues/1908),
[#&#8203;1909](https://redirect.github.com/dtolnay/syn/issues/1909))

###
[`v2.0.105`](https://redirect.github.com/dtolnay/syn/releases/tag/2.0.105)

[Compare
Source](https://redirect.github.com/dtolnay/syn/compare/2.0.104...2.0.105)

- Disallow "negative" inherent impls like `impl !T {}`
([#&#8203;1881](https://redirect.github.com/dtolnay/syn/issues/1881),
[rust-lang/rust#144386](https://redirect.github.com/rust-lang/rust/pull/144386))

</details>

---

### Configuration

📅 **Schedule**: Branch creation - "before 4am on Monday" (UTC),
Automerge - At any time (no schedule defined).

🚦 **Automerge**: Disabled by config. Please merge this manually once you
are satisfied.

♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the
rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about this update
again.

---

- [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check
this box

---

This PR was generated by [Mend Renovate](https://mend.io/renovate/).
View the [repository job
log](https://developer.mend.io/github/astral-sh/uv).

<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiI0MS44Mi43IiwidXBkYXRlZEluVmVyIjoiNDEuODIuNyIsInRhcmdldEJyYW5jaCI6Im1haW4iLCJsYWJlbHMiOlsiaW50ZXJuYWwiXX0=-->

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [syn](https://redirect.github.com/dtolnay/syn) |
workspace.dependencies | patch | `2.0.104` -> `2.0.106` |

---

> [!WARNING]
> Some dependencies could not be looked up. Check the Dependency
Dashboard for more information.

---

### Release Notes

<details>
<summary>dtolnay/syn (syn)</summary>

###
[`v2.0.106`](https://redirect.github.com/dtolnay/syn/releases/tag/2.0.106)

[Compare
Source](https://redirect.github.com/dtolnay/syn/compare/2.0.105...2.0.106)

- Replace `~const` syntax with `[const]` conditionally const syntax in
trait bounds
([#&astral-sh#8203;1896](https://redirect.github.com/dtolnay/syn/issues/1896),
[rust-lang/rust#139858](https://redirect.github.com/rust-lang/rust/pull/139858))
- Support conditionally const impl Trait types
([#&astral-sh#8203;1897](https://redirect.github.com/dtolnay/syn/issues/1897))
- Reject polarity modifier and lifetime binder used in the same trait
bound
([#&astral-sh#8203;1899](https://redirect.github.com/dtolnay/syn/issues/1899),
[rust-lang/rust#127054](https://redirect.github.com/rust-lang/rust/pull/127054))
- Parse const trait bounds with bound lifetimes
([#&astral-sh#8203;1902](https://redirect.github.com/dtolnay/syn/issues/1902))
- Parse bound lifetimes with lifetime bounds
([#&astral-sh#8203;1903](https://redirect.github.com/dtolnay/syn/issues/1903))
- Allow type parameters and const parameters in trait bounds and generic
closures
([#&astral-sh#8203;1904](https://redirect.github.com/dtolnay/syn/issues/1904),
[#&astral-sh#8203;1907](https://redirect.github.com/dtolnay/syn/issues/1907),
[#&astral-sh#8203;1908](https://redirect.github.com/dtolnay/syn/issues/1908),
[#&astral-sh#8203;1909](https://redirect.github.com/dtolnay/syn/issues/1909))

###
[`v2.0.105`](https://redirect.github.com/dtolnay/syn/releases/tag/2.0.105)

[Compare
Source](https://redirect.github.com/dtolnay/syn/compare/2.0.104...2.0.105)

- Disallow "negative" inherent impls like `impl !T {}`
([#&astral-sh#8203;1881](https://redirect.github.com/dtolnay/syn/issues/1881),
[rust-lang/rust#144386](https://redirect.github.com/rust-lang/rust/pull/144386))

</details>

---

### Configuration

📅 **Schedule**: Branch creation - "before 4am on Monday" (UTC),
Automerge - At any time (no schedule defined).

🚦 **Automerge**: Disabled by config. Please merge this manually once you
are satisfied.

♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the
rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about this update
again.

---

- [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check
this box

---

This PR was generated by [Mend Renovate](https://mend.io/renovate/).
View the [repository job
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<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiI0MS44Mi43IiwidXBkYXRlZEluVmVyIjoiNDEuODIuNyIsInRhcmdldEJyYW5jaCI6Im1haW4iLCJsYWJlbHMiOlsiaW50ZXJuYWwiXX0=-->

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

New const traits syntax

This PR only affects the AST and doesn't actually change anything semantically.

All occurrences of `~const` outside of libcore have been replaced by `[const]`. Within libcore we have to wait for rustfmt to be bumped in the bootstrap compiler. This will happen "automatically" (when rustfmt is run) during the bootstrap bump, as rustfmt converts `~const` into `[const]`. After this we can remove the `~const` support from the parser

Caveat discovered during impl: there is no legacy bare trait object recovery for `[const] Trait` as that snippet in type position goes down the slice /array parsing code and will error

r? ``@fee1-dead``

cc ``@nikomatsakis`` ``@traviscross`` ``@compiler-errors``

…r=fmease

Ping fmease on parser modifications

From time to time innocuous-seeming PRs get submitted and sometimes even approved that unbeknownst to their author and to reviewers change the grammar of (stable) Rust which would be a breaking change; often they only meant to tweak diagnostics.

I sometimes catch such PRs before they get merged but I want to make it a lot harder for them to slip through the cracks going forward.

I'm going to list recent examples to paint a picture (note: this is not about blame!):

1. rust-lang#149728 (review) (2026)
   * caught before merge but after approval
   * PR unapproved for now
2. rust-lang#152501 (2026)
   * caught after merge of rust-lang#149489
   * fixed & backported
3. rust-lang#152499 (2026)
   * caught after merge of rust-lang#149667
   * fixed & backported
4. rust-lang#151960 (comment) (2026)
   * caught right after submission
   * the approach was thus changed
5. rust-lang#148238 (2025)
   * caught after merge of rust-lang#118947
   * still unaddressed
6. rust-lang#144386 (review) (2025)
   * caught right after submission
   * crater & T-lang were activated by me
7. rust-lang#119042 (comment) (2023)
   * caught right after submission
   * the approach was thus changed
8. rust-lang#103534 (2022)
   * caught way later
   * partially addressed

Why not just post a note without pinging me? Well, due to them not failing CI and generally due to (friendly) botspam, such comments just get lost or sometimes even actively ignored.

Of course, I'm not able to catch everything. E.g., I didn't notice issue rust-lang#146417 before PR rust-lang#139858 was merged despite having skimmed its diff and more importantly, I as a reviewer missed the blatantly obvious rust-lang#144958 before merge.

Separately, off and on over the span of one year I've worked on a Rust parser that now has >99% accuracy/parity with rustc according to some metrics (this includes stable + unstable + internal syntax) and which I'm using to detect such regressions and issues in general among other things (e.g., rust-lang#152499 and rust-lang#152820 were found this way, more to come). I'm pretty invested, let's say.

r? me

…r=fmease

Ping fmease on parser modifications

From time to time innocuous-seeming PRs get submitted and sometimes even approved that unbeknownst to their author and to reviewers change the grammar of (stable) Rust which would be a breaking change; often they only meant to tweak diagnostics.

I sometimes catch such PRs before they get merged but I want to make it a lot harder for them to slip through the cracks going forward.

I'm going to list recent examples to paint a picture (note: this is not about blame!):

1. rust-lang#149728 (review) (2026)
   * caught before merge but after approval
   * PR unapproved for now
2. rust-lang#152501 (2026)
   * caught after merge of rust-lang#149489
   * fixed & backported
3. rust-lang#152499 (2026)
   * caught after merge of rust-lang#149667
   * fixed & backported
4. rust-lang#151960 (comment) (2026)
   * caught right after submission
   * the approach was thus changed
5. rust-lang#148238 (2025)
   * caught after merge of rust-lang#118947
   * still unaddressed
6. rust-lang#144386 (review) (2025)
   * caught right after submission
   * crater & T-lang were activated by me
7. rust-lang#119042 (comment) (2023)
   * caught right after submission
   * the approach was thus changed
8. rust-lang#103534 (2022)
   * caught way later
   * partially addressed

Why not just post a note without pinging me? Well, due to them not failing CI and generally due to (friendly) botspam, such comments just get lost or sometimes even actively ignored.

Of course, I'm not able to catch everything. E.g., I didn't notice issue rust-lang#146417 before PR rust-lang#139858 was merged despite having skimmed its diff and more importantly, I as a reviewer missed the blatantly obvious rust-lang#144958 before merge.

Separately, off and on over the span of one year I've worked on a Rust parser that now has >99% accuracy/parity with rustc according to some metrics (this includes stable + unstable + internal syntax) and which I'm using to detect such regressions and issues in general among other things (e.g., rust-lang#152499 and rust-lang#152820 were found this way, more to come). I'm pretty invested, let's say.

r? me

…r=fmease

Ping fmease on parser modifications

From time to time innocuous-seeming PRs get submitted and sometimes even approved that unbeknownst to their author and to reviewers change the grammar of (stable) Rust which would be a breaking change; often they only meant to tweak diagnostics.

I sometimes catch such PRs before they get merged but I want to make it a lot harder for them to slip through the cracks going forward.

I'm going to list recent examples to paint a picture (note: this is not about blame!):

1. rust-lang#149728 (review) (2026)
   * caught before merge but after approval
   * PR unapproved for now
2. rust-lang#152501 (2026)
   * caught after merge of rust-lang#149489
   * fixed & backported
3. rust-lang#152499 (2026)
   * caught after merge of rust-lang#149667
   * fixed & backported
4. rust-lang#151960 (comment) (2026)
   * caught right after submission
   * the approach was thus changed
5. rust-lang#148238 (2025)
   * caught after merge of rust-lang#118947
   * still unaddressed
6. rust-lang#144386 (review) (2025)
   * caught right after submission
   * crater & T-lang were activated by me
7. rust-lang#119042 (comment) (2023)
   * caught right after submission
   * the approach was thus changed
8. rust-lang#103534 (2022)
   * caught way later
   * partially addressed

Why not just post a note without pinging me? Well, due to them not failing CI and generally due to (friendly) botspam, such comments just get lost or sometimes even actively ignored.

Of course, I'm not able to catch everything. E.g., I didn't notice issue rust-lang#146417 before PR rust-lang#139858 was merged despite having skimmed its diff and more importantly, I as a reviewer missed the blatantly obvious rust-lang#144958 before merge.

Separately, off and on over the span of one year I've worked on a Rust parser that now has >99% accuracy/parity with rustc according to some metrics (this includes stable + unstable + internal syntax) and which I'm now using to detect such regressions and issues in general among other things (e.g., rust-lang#152499 and rust-lang#152820 were found this way, more to come). I'm pretty invested, let's say.

r? me