Make casts of pointers to trait objects stricter by WaffleLapkin · Pull Request #120248 · rust-lang/rust

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Jan 22, 2024

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bors added a commit to rust-lang-ci/rust that referenced this pull request

Jan 22, 2024
…r=<try>

Make casts of pointers to trait objects stricter

This is an attempt to `fix` rust-lang#120222 and rust-lang#120217.

cc `@oli-obk` `@compiler-errors` `@lcnr`

lukas-code

@rustbot rustbot added S-waiting-on-author

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Jan 31, 2024

bors added a commit to rust-lang-ci/rust that referenced this pull request

Feb 13, 2024
…r=<try>

Make casts of pointers to trait objects stricter

This is an attempt to `fix` rust-lang#120222 and rust-lang#120217.

This is done by adding restrictions on casting pointers to trait objects. Currently the restriction is
> When casting `*const X<dyn A>` -> `*const Y<dyn B>`, if `B` has a principal trait, `dyn A + 'erased: Unsize<dyn B + 'erased>` must hold

This ensures that
1. Principal trait's generic arguments match (no `*const dyn Tr<A>` -> `*const dyn Tr<B>` casts, which are a problem for [rust-lang#120222](rust-lang#120222))
2. Principal trait's lifetime arguments match (no `*const dyn Tr<'a>` -> `*const dyn Tr<'b>` casts, which are a problem for [rust-lang#120217](rust-lang#120217))
3. No auto traits can be _added_ (this is a problem for arbitrary self types, see [this comment](rust-lang#120248 (comment)))

Some notes:
 - We only care about the metadata/last field, so you can still cast `*const dyn T` to `*const WithHeader<dyn T>`, etc
- The lifetime of the trait object itself (`dyn A + 'lt`) is not checked, so you can still cast `*mut FnOnce() + '_` to `*mut FnOnce() + 'static`, etc
  - This feels fishy, but I couldn't come up with a reason it must be checked
- The new checks are only done if `B` has a principal, so you can still do any kinds of cast, if the target only has auto traits
  - This is because auto traits are not enough to get unsoundness issues that this PR fixes
  - ...and so it makes sense to minimize breakage

The plan is to, ~~once the checks are properly implemented~~, run crate to determine how much damage does this do.

The diagnostics are currently not great, to say the least, but as far as I can tell this correctly fixes the issues.

cc `@oli-obk` `@compiler-errors` `@lcnr`

tmeijn pushed a commit to tmeijn/dotfiles that referenced this pull request

Sep 11, 2024
This MR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [rust](https://github.com/rust-lang/rust) | minor | `1.80.1` -> `1.81.0` |

MR created with the help of [el-capitano/tools/renovate-bot](https://gitlab.com/el-capitano/tools/renovate-bot).

**Proposed changes to behavior should be submitted there as MRs.**

---

### Release Notes

<details>
<summary>rust-lang/rust (rust)</summary>

### [`v1.81.0`](https://github.com/rust-lang/rust/blob/HEAD/RELEASES.md#Version-1810-2024-09-05)

[Compare Source](rust-lang/rust@1.80.1...1.81.0)

\==========================

<a id="1.81.0-Language"></a>

## Language

-   [Abort on uncaught panics in `extern "C"` functions.](rust-lang/rust#116088)
-   [Fix ambiguous cases of multiple `&` in elided self lifetimes.](rust-lang/rust#117967)
-   [Stabilize `#[expect]` for lints (RFC 2383),](rust-lang/rust#120924) like `#[allow]` with a warning if the lint is *not* fulfilled.
-   [Change method resolution to constrain hidden types instead of rejecting method candidates.](rust-lang/rust#123962)
-   [Bump `elided_lifetimes_in_associated_constant` to deny.](rust-lang/rust#124211)
-   [`offset_from`: always allow pointers to point to the same address.](rust-lang/rust#124921)
-   [Allow constraining opaque types during subtyping in the trait system.](rust-lang/rust#125447)
-   [Allow constraining opaque types during various unsizing casts.](rust-lang/rust#125610)
-   [Deny keyword lifetimes pre-expansion.](rust-lang/rust#126762)

<a id="1.81.0-Compiler"></a>

## Compiler

-   [Make casts of pointers to trait objects stricter.](rust-lang/rust#120248)
-   [Check alias args for well-formedness even if they have escaping bound vars.](rust-lang/rust#123737)
-   [Deprecate no-op codegen option `-Cinline-threshold=...`.](rust-lang/rust#124712)
-   [Re-implement a type-size based limit.](rust-lang/rust#125507)
-   [Properly account for alignment in `transmute` size checks.](rust-lang/rust#125740)
-   [Remove the `box_pointers` lint.](rust-lang/rust#126018)
-   [Ensure the interpreter checks bool/char for validity when they are used in a cast.](rust-lang/rust#126265)
-   [Improve coverage instrumentation for functions containing nested items.](rust-lang/rust#127199)
-   Target changes:
    -   [Add Tier 3 `no_std` Xtensa targets:](rust-lang/rust#125141) `xtensa-esp32-none-elf`, `xtensa-esp32s2-none-elf`, `xtensa-esp32s3-none-elf`
    -   [Add Tier 3 `std` Xtensa targets:](rust-lang/rust#126380) `xtensa-esp32-espidf`, `xtensa-esp32s2-espidf`, `xtensa-esp32s3-espidf`
    -   [Add Tier 3 i686 Redox OS target:](rust-lang/rust#126192) `i686-unknown-redox`
    -   [Promote `arm64ec-pc-windows-msvc` to Tier 2.](rust-lang/rust#126039)
    -   [Promote `loongarch64-unknown-linux-musl` to Tier 2 with host tools.](rust-lang/rust#126298)
    -   [Enable full tools and profiler for LoongArch Linux targets.](rust-lang/rust#127078)
    -   [Unconditionally warn on usage of `wasm32-wasi`.](rust-lang/rust#126662) (see compatibility note below)
    -   Refer to Rust's \[platform support page]\[platform-support-doc] for more information on Rust's tiered platform support.

<a id="1.81.0-Libraries"></a>

## Libraries

-   [Split core's `PanicInfo` and std's `PanicInfo`.](rust-lang/rust#115974) (see compatibility note below)
-   [Generalize `{Rc,Arc}::make_mut()` to unsized types.](rust-lang/rust#116113)
-   [Replace sort implementations with stable `driftsort` and unstable `ipnsort`.](rust-lang/rust#124032) All `slice::sort*` and `slice::select_nth*` methods are expected to see significant performance improvements. See the [research project](https://github.com/Voultapher/sort-research-rs) for more details.
-   [Document behavior of `create_dir_all` with respect to empty paths.](rust-lang/rust#125112)
-   [Fix interleaved output in the default panic hook when multiple threads panic simultaneously.](rust-lang/rust#127397)

<a id="1.81.0-Stabilized-APIs"></a>

## Stabilized APIs

-   [`core::error`](https://doc.rust-lang.org/stable/core/error/index.html)
-   [`hint::assert_unchecked`](https://doc.rust-lang.org/stable/core/hint/fn.assert_unchecked.html)
-   [`fs::exists`](https://doc.rust-lang.org/stable/std/fs/fn.exists.html)
-   [`AtomicBool::fetch_not`](https://doc.rust-lang.org/stable/core/sync/atomic/struct.AtomicBool.html#method.fetch_not)
-   [`Duration::abs_diff`](https://doc.rust-lang.org/stable/core/time/struct.Duration.html#method.abs_diff)
-   [`IoSlice::advance`](https://doc.rust-lang.org/stable/std/io/struct.IoSlice.html#method.advance)
-   [`IoSlice::advance_slices`](https://doc.rust-lang.org/stable/std/io/struct.IoSlice.html#method.advance_slices)
-   [`IoSliceMut::advance`](https://doc.rust-lang.org/stable/std/io/struct.IoSliceMut.html#method.advance)
-   [`IoSliceMut::advance_slices`](https://doc.rust-lang.org/stable/std/io/struct.IoSliceMut.html#method.advance_slices)
-   [`PanicHookInfo`](https://doc.rust-lang.org/stable/std/panic/struct.PanicHookInfo.html)
-   [`PanicInfo::message`](https://doc.rust-lang.org/stable/core/panic/struct.PanicInfo.html#method.message)
-   [`PanicMessage`](https://doc.rust-lang.org/stable/core/panic/struct.PanicMessage.html)

These APIs are now stable in const contexts:

-   [`char::from_u32_unchecked`](https://doc.rust-lang.org/stable/core/char/fn.from_u32\_unchecked.html) (function)
-   [`char::from_u32_unchecked`](https://doc.rust-lang.org/stable/core/primitive.char.html#method.from_u32\_unchecked) (method)
-   [`CStr::count_bytes`](https://doc.rust-lang.org/stable/core/ffi/c_str/struct.CStr.html#method.count_bytes)
-   [`CStr::from_ptr`](https://doc.rust-lang.org/stable/core/ffi/c_str/struct.CStr.html#method.from_ptr)

<a id="1.81.0-Cargo"></a>

## Cargo

-   [Generated `.cargo_vcs_info.json` is always included, even when `--allow-dirty` is passed.](rust-lang/cargo#13960)
-   [Disallow `package.license-file` and `package.readme` pointing to non-existent files during packaging.](rust-lang/cargo#13921)
-   [Disallow passing `--release`/`--debug` flag along with the `--profile` flag.](rust-lang/cargo#13971)
-   [Remove `lib.plugin` key support in `Cargo.toml`. Rust plugin support has been deprecated for four years and was removed in 1.75.0.](rust-lang/cargo#13902)

<a id="1.81.0-Compatibility-Notes"></a>

## Compatibility Notes

-   Usage of the `wasm32-wasi` target will now issue a compiler warning and request users switch to the `wasm32-wasip1` target instead. Both targets are the same, `wasm32-wasi` is only being renamed, and this [change to the WASI target](https://blog.rust-lang.org/2024/04/09/updates-to-rusts-wasi-targets.html) is being done to enable removing `wasm32-wasi` in January 2025.

-   We have renamed `std::panic::PanicInfo` to `std::panic::PanicHookInfo`. The old name will continue to work as an alias, but will result in a deprecation warning starting in Rust 1.82.0.

    `core::panic::PanicInfo` will remain unchanged, however, as this is now a *different type*.

    The reason is that these types have different roles: `std::panic::PanicHookInfo` is the argument to the [panic hook](https://doc.rust-lang.org/stable/std/panic/fn.set_hook.html) in std context (where panics can have an arbitrary payload), while `core::panic::PanicInfo` is the argument to the [`#[panic_handler]`](https://doc.rust-lang.org/nomicon/panic-handler.html) in no_std context (where panics always carry a formatted *message*). Separating these types allows us to add more useful methods to these types, such as `std::panic::PanicHookInfo::payload_as_str()` and `core::panic::PanicInfo::message()`.

-   The new sort implementations may panic if a type's implementation of [`Ord`](https://doc.rust-lang.org/std/cmp/trait.Ord.html) (or the given comparison function) does not implement a [total order](https://en.wikipedia.org/wiki/Total_order) as the trait requires. `Ord`'s supertraits (`PartialOrd`, `Eq`, and `PartialEq`) must also be consistent. The previous implementations would not "notice" any problem, but the new implementations have a good chance of detecting inconsistencies, throwing a panic rather than returning knowingly unsorted data.

-   [In very rare cases, a change in the internal evaluation order of the trait
    solver may result in new fatal overflow errors.](rust-lang/rust#126128)

<a id="1.81.0-Internal-Changes"></a>

## Internal Changes

These changes do not affect any public interfaces of Rust, but they represent
significant improvements to the performance or internals of rustc and related
tools.

-   [Add a Rust-for Linux `auto` CI job to check kernel builds.](rust-lang/rust#125209)

</details>

---

### Configuration

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

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wip-sync pushed a commit to NetBSD/pkgsrc-wip that referenced this pull request

Sep 22, 2024
Pkgsrc changes:
 * Adapt patches, apply to new vendored crates where needed.
 * Back-port rust pull request 130110, "make dist vendoring configurable"
 * Disable "dist vendoring", otherwise cargo would try to access
   the network during the build phase.

Upstream changes:

Version 1.81.0 (2024-09-05)
==========================

Language
--------

- [Abort on uncaught panics in `extern "C"` functions.]
  (rust-lang/rust#116088)
- [Fix ambiguous cases of multiple `&` in elided self lifetimes.]
  (rust-lang/rust#117967)
- [Stabilize `#[expect]` for lints (RFC 2383),]
  (rust-lang/rust#120924) like `#[allow]`
  with a warning if the lint is _not_ fulfilled.
- [Change method resolution to constrain hidden types instead of
  rejecting method candidates.]
  (rust-lang/rust#123962)
- [Bump `elided_lifetimes_in_associated_constant` to deny.]
  (rust-lang/rust#124211)
- [`offset_from`: always allow pointers to point to the same
  address.] (rust-lang/rust#124921)
- [Allow constraining opaque types during subtyping in the trait
  system.] (rust-lang/rust#125447)
- [Allow constraining opaque types during various unsizing casts.]
  (rust-lang/rust#125610)
- [Deny keyword lifetimes pre-expansion.]
  (rust-lang/rust#126762)

Compiler
--------

- [Make casts of pointers to trait objects stricter.]
  (rust-lang/rust#120248)
- [Check alias args for well-formedness even if they have escaping
  bound vars.] (rust-lang/rust#123737)
- [Deprecate no-op codegen option `-Cinline-threshold=...`.]
  (rust-lang/rust#124712)
- [Re-implement a type-size based limit.]
  (rust-lang/rust#125507)
- [Properly account for alignment in `transmute` size checks.]
  (rust-lang/rust#125740)
- [Remove the `box_pointers` lint.]
  (rust-lang/rust#126018)
- [Ensure the interpreter checks bool/char for validity when they
  are used in a cast.] (rust-lang/rust#126265)
- [Improve coverage instrumentation for functions containing nested
  items.] (rust-lang/rust#127199)
- Target changes:
  - [Add Tier 3 `no_std` Xtensa targets:]
    (rust-lang/rust#125141) `xtensa-esp32-none-elf`,
    `xtensa-esp32s2-none-elf`, `xtensa-esp32s3-none-elf`
  - [Add Tier 3 `std` Xtensa targets:]
    (rust-lang/rust#126380) `xtensa-esp32-espidf`,
    `xtensa-esp32s2-espidf`, `xtensa-esp32s3-espidf`
  - [Add Tier 3 i686 Redox OS target:]
    (rust-lang/rust#126192) `i686-unknown-redox`
  - [Promote `arm64ec-pc-windows-msvc` to Tier 2.]
    (rust-lang/rust#126039)
  - [Promote `wasm32-wasip2` to Tier 2.]
    (rust-lang/rust#126967)
  - [Promote `loongarch64-unknown-linux-musl` to Tier 2 with host
    tools.] (rust-lang/rust#126298)
  - [Enable full tools and profiler for LoongArch Linux targets.]
    (rust-lang/rust#127078)
  - [Unconditionally warn on usage of `wasm32-wasi`.]
    (rust-lang/rust#126662) (see compatibility
    note below)
  - Refer to Rust's [platform support page][platform-support-doc]
    for more information on Rust's tiered platform support.

Libraries
---------

- [Split core's `PanicInfo` and std's `PanicInfo`.]
  (rust-lang/rust#115974) (see compatibility
  note below)
- [Generalize `{Rc,Arc}::make_mut()` to unsized types.]
  (rust-lang/rust#116113)
- [Replace sort implementations with stable `driftsort` and unstable
  `ipnsort`.] (rust-lang/rust#124032) All
  `slice::sort*` and `slice::select_nth*` methods are expected to
  see significant performance improvements. See the [research
  project] (https://github.com/Voultapher/sort-research-rs) for
  more details.
- [Document behavior of `create_dir_all` with respect to empty
  paths.] (rust-lang/rust#125112)
- [Fix interleaved output in the default panic hook when multiple
  threads panic simultaneously.]
  (rust-lang/rust#127397)
- Fix `Command`'s batch files argument escaping not working when
  file name has trailing whitespace or periods (CVE-2024-43402).

Stabilized APIs
---------------

- [`core::error`] (https://doc.rust-lang.org/stable/core/error/index.html)
- [`hint::assert_unchecked`]
  (https://doc.rust-lang.org/stable/core/hint/fn.assert_unchecked.html)
- [`fs::exists`] (https://doc.rust-lang.org/stable/std/fs/fn.exists.html)
- [`AtomicBool::fetch_not`]
  (https://doc.rust-lang.org/stable/core/sync/atomic/struct.AtomicBool.html#method.fetch_not)
- [`Duration::abs_diff`]
  (https://doc.rust-lang.org/stable/core/time/struct.Duration.html#method.abs_diff)
- [`IoSlice::advance`]
  (https://doc.rust-lang.org/stable/std/io/struct.IoSlice.html#method.advance)
- [`IoSlice::advance_slices`]
  (https://doc.rust-lang.org/stable/std/io/struct.IoSlice.html#method.advance_slices)
- [`IoSliceMut::advance`]
  (https://doc.rust-lang.org/stable/std/io/struct.IoSliceMut.html#method.advance)
- [`IoSliceMut::advance_slices`]
  (https://doc.rust-lang.org/stable/std/io/struct.IoSliceMut.html#method.advance_slices)
- [`PanicHookInfo`]
  (https://doc.rust-lang.org/stable/std/panic/struct.PanicHookInfo.html)
- [`PanicInfo::message`]
  (https://doc.rust-lang.org/stable/core/panic/struct.PanicInfo.html#method.message)
- [`PanicMessage`]
  (https://doc.rust-lang.org/stable/core/panic/struct.PanicMessage.html)

These APIs are now stable in const contexts:

- [`char::from_u32_unchecked`]
  (https://doc.rust-lang.org/stable/core/char/fn.from_u32_unchecked.html)
  (function)
- [`char::from_u32_unchecked`]
  (https://doc.rust-lang.org/stable/core/primitive.char.html#method.from_u32_unchecked)
  (method)
- [`CStr::count_bytes`]
  (https://doc.rust-lang.org/stable/core/ffi/c_str/struct.CStr.html#method.count_bytes)
- [`CStr::from_ptr`]
  (https://doc.rust-lang.org/stable/core/ffi/c_str/struct.CStr.html#method.from_ptr)

Cargo
-----

- [Generated `.cargo_vcs_info.json` is always included, even when
  `--allow-dirty` is passed.]
  (rust-lang/cargo#13960)
- [Disallow `package.license-file` and `package.readme` pointing
  to non-existent files during packaging.]
  (rust-lang/cargo#13921)
- [Disallow passing `--release`/`--debug` flag along with the
  `--profile` flag.] (rust-lang/cargo#13971)
- [Remove `lib.plugin` key support in `Cargo.toml`. Rust plugin
  support has been deprecated for four years and was removed in
  1.75.0.] (rust-lang/cargo#13902)

Compatibility Notes
-------------------

* Usage of the `wasm32-wasi` target will now issue a compiler
  warning and request users switch to the `wasm32-wasip1` target
  instead. Both targets are the same, `wasm32-wasi` is only being
  renamed, and this [change to the WASI target]
  (https://blog.rust-lang.org/2024/04/09/updates-to-rusts-wasi-targets.html)
  is being done to enable removing `wasm32-wasi` in January 2025.

* We have renamed `std::panic::PanicInfo` to `std::panic::PanicHookInfo`.
  The old name will continue to work as an alias, but will result in
  a deprecation warning starting in Rust 1.82.0.

  `core::panic::PanicInfo` will remain unchanged, however, as this
  is now a *different type*.

  The reason is that these types have different roles:
  `std::panic::PanicHookInfo` is the argument to the [panic
  hook](https://doc.rust-lang.org/stable/std/panic/fn.set_hook.html)
  in std context (where panics can have an arbitrary payload),
  while `core::panic::PanicInfo` is the argument to the
  [`#[panic_handler]`](https://doc.rust-lang.org/nomicon/panic-handler.html)
  in no_std context (where panics always carry a formatted *message*).
  Separating these types allows us to add more useful methods to
  these types, such as `std::panic::PanicHookInfo::payload_as_str()`
  and `core::panic::PanicInfo::message()`.

* The new sort implementations may panic if a type's implementation
  of [`Ord`](https://doc.rust-lang.org/std/cmp/trait.Ord.html) (or
  the given comparison function) does not implement a [total
  order](https://en.wikipedia.org/wiki/Total_order) as the trait
  requires. `Ord`'s supertraits (`PartialOrd`, `Eq`, and `PartialEq`)
  must also be consistent. The previous implementations would not
  "notice" any problem, but the new implementations have a good chance
  of detecting inconsistencies, throwing a panic rather than returning
  knowingly unsorted data.
* [In very rare cases, a change in the internal evaluation order of the trait
  solver may result in new fatal overflow errors.]
  (rust-lang/rust#126128)

Internal Changes
----------------

These changes do not affect any public interfaces of Rust, but they
represent significant improvements to the performance or internals
of rustc and related tools.

- [Add a Rust-for Linux `auto` CI job to check kernel builds.]
  (rust-lang/rust#125209)

tgross35 added a commit to tgross35/rust that referenced this pull request

Sep 24, 2024
…leLapkin

improve compile errors for invalid ptr-to-ptr casts with trait objects

This is a follow-up to rust-lang#120248 to improve some of its error messages.

1. Make the borrowcheck error for "type annotation requires that x must outlive y" actually point at the type annotation, i.e. the type `T` in a `x as T` cast. This makes the error more consistent with other errors caused by type annotation in other places, such as
```text
error: lifetime may not live long enough
 --> src/lib.rs:4:12
  |
3 | fn bar(a: &i32) {
  |           - let's call the lifetime of this reference `'1`
4 |     let b: &'static i32 = a;
  |            ^^^^^^^^^^^^ type annotation requires that `'1` must outlive `'static`
```

2. Don't say "cast" when we actually mean "coercion" and give borrowcheck errors from actual casts (which is currently just the check added in rust-lang#120248) a higher priority than ones from coercions. This can improve the errors for ptr-to-ptr cast between trait objects because they are are lowered as an upcast "unsizing" coercion if possible (which may be the identity upcast) followed by the actual cast.

3. Bring back the old "casting X as Y is invalid" message for type mismatch in the principals and reword the "vtable kinds may not match" message to more accurately describe the pointer metadata and not refer to "vtables" if the metadata is unknown.

fixes rust-lang#130030

r? `@WaffleLapkin` but feel free to reassign

rust-timer added a commit to rust-lang-ci/rust that referenced this pull request

Sep 25, 2024
Rollup merge of rust-lang#130234 - lukas-code:ptr-cast-errors, r=WaffleLapkin

improve compile errors for invalid ptr-to-ptr casts with trait objects

This is a follow-up to rust-lang#120248 to improve some of its error messages.

1. Make the borrowcheck error for "type annotation requires that x must outlive y" actually point at the type annotation, i.e. the type `T` in a `x as T` cast. This makes the error more consistent with other errors caused by type annotation in other places, such as
```text
error: lifetime may not live long enough
 --> src/lib.rs:4:12
  |
3 | fn bar(a: &i32) {
  |           - let's call the lifetime of this reference `'1`
4 |     let b: &'static i32 = a;
  |            ^^^^^^^^^^^^ type annotation requires that `'1` must outlive `'static`
```

2. Don't say "cast" when we actually mean "coercion" and give borrowcheck errors from actual casts (which is currently just the check added in rust-lang#120248) a higher priority than ones from coercions. This can improve the errors for ptr-to-ptr cast between trait objects because they are are lowered as an upcast "unsizing" coercion if possible (which may be the identity upcast) followed by the actual cast.

3. Bring back the old "casting X as Y is invalid" message for type mismatch in the principals and reword the "vtable kinds may not match" message to more accurately describe the pointer metadata and not refer to "vtables" if the metadata is unknown.

fixes rust-lang#130030

r? `@WaffleLapkin` but feel free to reassign

github-actions bot pushed a commit to rust-lang/miri that referenced this pull request

Sep 25, 2024
improve compile errors for invalid ptr-to-ptr casts with trait objects

This is a follow-up to rust-lang/rust#120248 to improve some of its error messages.

1. Make the borrowcheck error for "type annotation requires that x must outlive y" actually point at the type annotation, i.e. the type `T` in a `x as T` cast. This makes the error more consistent with other errors caused by type annotation in other places, such as
```text
error: lifetime may not live long enough
 --> src/lib.rs:4:12
  |
3 | fn bar(a: &i32) {
  |           - let's call the lifetime of this reference `'1`
4 |     let b: &'static i32 = a;
  |            ^^^^^^^^^^^^ type annotation requires that `'1` must outlive `'static`
```

2. Don't say "cast" when we actually mean "coercion" and give borrowcheck errors from actual casts (which is currently just the check added in rust-lang/rust#120248) a higher priority than ones from coercions. This can improve the errors for ptr-to-ptr cast between trait objects because they are are lowered as an upcast "unsizing" coercion if possible (which may be the identity upcast) followed by the actual cast.

3. Bring back the old "casting X as Y is invalid" message for type mismatch in the principals and reword the "vtable kinds may not match" message to more accurately describe the pointer metadata and not refer to "vtables" if the metadata is unknown.

fixes rust-lang/rust#130030

r? `@WaffleLapkin` but feel free to reassign

netbsd-srcmastr pushed a commit to NetBSD/pkgsrc that referenced this pull request

Nov 24, 2024
Pkgsrc changes:
 * Adapt patches, apply to new vendored crates where needed.
 * Back-port rust pull request 130110, "make dist vendoring configurable"
 * Disable "dist vendoring", otherwise cargo would try to access
   the network during the build phase.

Upstream changes:

Version 1.81.0 (2024-09-05)
==========================

Language
--------

- [Abort on uncaught panics in `extern "C"` functions.]
  (rust-lang/rust#116088)
- [Fix ambiguous cases of multiple `&` in elided self lifetimes.]
  (rust-lang/rust#117967)
- [Stabilize `#[expect]` for lints (RFC 2383),]
  (rust-lang/rust#120924) like `#[allow]`
  with a warning if the lint is _not_ fulfilled.
- [Change method resolution to constrain hidden types instead of
  rejecting method candidates.]
  (rust-lang/rust#123962)
- [Bump `elided_lifetimes_in_associated_constant` to deny.]
  (rust-lang/rust#124211)
- [`offset_from`: always allow pointers to point to the same
  address.] (rust-lang/rust#124921)
- [Allow constraining opaque types during subtyping in the trait
  system.] (rust-lang/rust#125447)
- [Allow constraining opaque types during various unsizing casts.]
  (rust-lang/rust#125610)
- [Deny keyword lifetimes pre-expansion.]
  (rust-lang/rust#126762)

Compiler
--------

- [Make casts of pointers to trait objects stricter.]
  (rust-lang/rust#120248)
- [Check alias args for well-formedness even if they have escaping
  bound vars.] (rust-lang/rust#123737)
- [Deprecate no-op codegen option `-Cinline-threshold=...`.]
  (rust-lang/rust#124712)
- [Re-implement a type-size based limit.]
  (rust-lang/rust#125507)
- [Properly account for alignment in `transmute` size checks.]
  (rust-lang/rust#125740)
- [Remove the `box_pointers` lint.]
  (rust-lang/rust#126018)
- [Ensure the interpreter checks bool/char for validity when they
  are used in a cast.] (rust-lang/rust#126265)
- [Improve coverage instrumentation for functions containing nested
  items.] (rust-lang/rust#127199)
- Target changes:
  - [Add Tier 3 `no_std` Xtensa targets:]
    (rust-lang/rust#125141) `xtensa-esp32-none-elf`,
    `xtensa-esp32s2-none-elf`, `xtensa-esp32s3-none-elf`
  - [Add Tier 3 `std` Xtensa targets:]
    (rust-lang/rust#126380) `xtensa-esp32-espidf`,
    `xtensa-esp32s2-espidf`, `xtensa-esp32s3-espidf`
  - [Add Tier 3 i686 Redox OS target:]
    (rust-lang/rust#126192) `i686-unknown-redox`
  - [Promote `arm64ec-pc-windows-msvc` to Tier 2.]
    (rust-lang/rust#126039)
  - [Promote `wasm32-wasip2` to Tier 2.]
    (rust-lang/rust#126967)
  - [Promote `loongarch64-unknown-linux-musl` to Tier 2 with host
    tools.] (rust-lang/rust#126298)
  - [Enable full tools and profiler for LoongArch Linux targets.]
    (rust-lang/rust#127078)
  - [Unconditionally warn on usage of `wasm32-wasi`.]
    (rust-lang/rust#126662) (see compatibility
    note below)
  - Refer to Rust's [platform support page][platform-support-doc]
    for more information on Rust's tiered platform support.

Libraries
---------

- [Split core's `PanicInfo` and std's `PanicInfo`.]
  (rust-lang/rust#115974) (see compatibility
  note below)
- [Generalize `{Rc,Arc}::make_mut()` to unsized types.]
  (rust-lang/rust#116113)
- [Replace sort implementations with stable `driftsort` and unstable
  `ipnsort`.] (rust-lang/rust#124032) All
  `slice::sort*` and `slice::select_nth*` methods are expected to
  see significant performance improvements. See the [research
  project] (https://github.com/Voultapher/sort-research-rs) for
  more details.
- [Document behavior of `create_dir_all` with respect to empty
  paths.] (rust-lang/rust#125112)
- [Fix interleaved output in the default panic hook when multiple
  threads panic simultaneously.]
  (rust-lang/rust#127397)
- Fix `Command`'s batch files argument escaping not working when
  file name has trailing whitespace or periods (CVE-2024-43402).

Stabilized APIs
---------------

- [`core::error`] (https://doc.rust-lang.org/stable/core/error/index.html)
- [`hint::assert_unchecked`]
  (https://doc.rust-lang.org/stable/core/hint/fn.assert_unchecked.html)
- [`fs::exists`] (https://doc.rust-lang.org/stable/std/fs/fn.exists.html)
- [`AtomicBool::fetch_not`]
  (https://doc.rust-lang.org/stable/core/sync/atomic/struct.AtomicBool.html#method.fetch_not)
- [`Duration::abs_diff`]
  (https://doc.rust-lang.org/stable/core/time/struct.Duration.html#method.abs_diff)
- [`IoSlice::advance`]
  (https://doc.rust-lang.org/stable/std/io/struct.IoSlice.html#method.advance)
- [`IoSlice::advance_slices`]
  (https://doc.rust-lang.org/stable/std/io/struct.IoSlice.html#method.advance_slices)
- [`IoSliceMut::advance`]
  (https://doc.rust-lang.org/stable/std/io/struct.IoSliceMut.html#method.advance)
- [`IoSliceMut::advance_slices`]
  (https://doc.rust-lang.org/stable/std/io/struct.IoSliceMut.html#method.advance_slices)
- [`PanicHookInfo`]
  (https://doc.rust-lang.org/stable/std/panic/struct.PanicHookInfo.html)
- [`PanicInfo::message`]
  (https://doc.rust-lang.org/stable/core/panic/struct.PanicInfo.html#method.message)
- [`PanicMessage`]
  (https://doc.rust-lang.org/stable/core/panic/struct.PanicMessage.html)

These APIs are now stable in const contexts:

- [`char::from_u32_unchecked`]
  (https://doc.rust-lang.org/stable/core/char/fn.from_u32_unchecked.html)
  (function)
- [`char::from_u32_unchecked`]
  (https://doc.rust-lang.org/stable/core/primitive.char.html#method.from_u32_unchecked)
  (method)
- [`CStr::count_bytes`]
  (https://doc.rust-lang.org/stable/core/ffi/c_str/struct.CStr.html#method.count_bytes)
- [`CStr::from_ptr`]
  (https://doc.rust-lang.org/stable/core/ffi/c_str/struct.CStr.html#method.from_ptr)

Cargo
-----

- [Generated `.cargo_vcs_info.json` is always included, even when
  `--allow-dirty` is passed.]
  (rust-lang/cargo#13960)
- [Disallow `package.license-file` and `package.readme` pointing
  to non-existent files during packaging.]
  (rust-lang/cargo#13921)
- [Disallow passing `--release`/`--debug` flag along with the
  `--profile` flag.] (rust-lang/cargo#13971)
- [Remove `lib.plugin` key support in `Cargo.toml`. Rust plugin
  support has been deprecated for four years and was removed in
  1.75.0.] (rust-lang/cargo#13902)

Compatibility Notes
-------------------

* Usage of the `wasm32-wasi` target will now issue a compiler
  warning and request users switch to the `wasm32-wasip1` target
  instead. Both targets are the same, `wasm32-wasi` is only being
  renamed, and this [change to the WASI target]
  (https://blog.rust-lang.org/2024/04/09/updates-to-rusts-wasi-targets.html)
  is being done to enable removing `wasm32-wasi` in January 2025.

* We have renamed `std::panic::PanicInfo` to `std::panic::PanicHookInfo`.
  The old name will continue to work as an alias, but will result in
  a deprecation warning starting in Rust 1.82.0.

  `core::panic::PanicInfo` will remain unchanged, however, as this
  is now a *different type*.

  The reason is that these types have different roles:
  `std::panic::PanicHookInfo` is the argument to the [panic
  hook](https://doc.rust-lang.org/stable/std/panic/fn.set_hook.html)
  in std context (where panics can have an arbitrary payload),
  while `core::panic::PanicInfo` is the argument to the
  [`#[panic_handler]`](https://doc.rust-lang.org/nomicon/panic-handler.html)
  in no_std context (where panics always carry a formatted *message*).
  Separating these types allows us to add more useful methods to
  these types, such as `std::panic::PanicHookInfo::payload_as_str()`
  and `core::panic::PanicInfo::message()`.

* The new sort implementations may panic if a type's implementation
  of [`Ord`](https://doc.rust-lang.org/std/cmp/trait.Ord.html) (or
  the given comparison function) does not implement a [total
  order](https://en.wikipedia.org/wiki/Total_order) as the trait
  requires. `Ord`'s supertraits (`PartialOrd`, `Eq`, and `PartialEq`)
  must also be consistent. The previous implementations would not
  "notice" any problem, but the new implementations have a good chance
  of detecting inconsistencies, throwing a panic rather than returning
  knowingly unsorted data.
* [In very rare cases, a change in the internal evaluation order of the trait
  solver may result in new fatal overflow errors.]
  (rust-lang/rust#126128)

Internal Changes
----------------

These changes do not affect any public interfaces of Rust, but they
represent significant improvements to the performance or internals
of rustc and related tools.

- [Add a Rust-for Linux `auto` CI job to check kernel builds.]
  (rust-lang/rust#125209)

jieyouxu added a commit to jieyouxu/rust that referenced this pull request

Mar 9, 2025
…r=compiler-errors

Allow `*const W<dyn A> -> *const dyn A` ptr cast

Followup of rust-lang#120248 (comment).

This PR allows casting pointers from something wrapping a trait object, to the trait object, i.e. `*const W<dyn A> -> *const dyn A` where `W` is `struct W<T: ?Sized>(T);`.

r? compiler-errors

Fixes rust-lang#128625

matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request

Mar 9, 2025
…r=compiler-errors

Allow `*const W<dyn A> -> *const dyn A` ptr cast

Followup of rust-lang#120248 (comment).

This PR allows casting pointers from something wrapping a trait object, to the trait object, i.e. `*const W<dyn A> -> *const dyn A` where `W` is `struct W<T: ?Sized>(T);`.

r? compiler-errors

Fixes rust-lang#128625

rust-timer added a commit to rust-lang-ci/rust that referenced this pull request

Mar 9, 2025
Rollup merge of rust-lang#136127 - WaffleLapkin:dyn_ptr_unwrap_cast, r=compiler-errors

Allow `*const W<dyn A> -> *const dyn A` ptr cast

Followup of rust-lang#120248 (comment).

This PR allows casting pointers from something wrapping a trait object, to the trait object, i.e. `*const W<dyn A> -> *const dyn A` where `W` is `struct W<T: ?Sized>(T);`.

r? compiler-errors

Fixes rust-lang#128625

@traviscross traviscross added T-lang

Relevant to the language team

I-lang-radar

Items that are on lang's radar and will need eventual work or consideration.

labels

Jan 16, 2026

christian-schilling pushed a commit to christian-schilling/rustc_codegen_cranelift that referenced this pull request

Jan 27, 2026
improve compile errors for invalid ptr-to-ptr casts with trait objects

This is a follow-up to rust-lang/rust#120248 to improve some of its error messages.

1. Make the borrowcheck error for "type annotation requires that x must outlive y" actually point at the type annotation, i.e. the type `T` in a `x as T` cast. This makes the error more consistent with other errors caused by type annotation in other places, such as
```text
error: lifetime may not live long enough
 --> src/lib.rs:4:12
  |
3 | fn bar(a: &i32) {
  |           - let's call the lifetime of this reference `'1`
4 |     let b: &'static i32 = a;
  |            ^^^^^^^^^^^^ type annotation requires that `'1` must outlive `'static`
```

2. Don't say "cast" when we actually mean "coercion" and give borrowcheck errors from actual casts (which is currently just the check added in rust-lang/rust#120248) a higher priority than ones from coercions. This can improve the errors for ptr-to-ptr cast between trait objects because they are are lowered as an upcast "unsizing" coercion if possible (which may be the identity upcast) followed by the actual cast.

3. Bring back the old "casting X as Y is invalid" message for type mismatch in the principals and reword the "vtable kinds may not match" message to more accurately describe the pointer metadata and not refer to "vtables" if the metadata is unknown.

fixes rust-lang/rust#130030

r? `@WaffleLapkin` but feel free to reassign

christian-schilling pushed a commit to christian-schilling/rustc_codegen_cranelift that referenced this pull request

Jan 27, 2026
improve compile errors for invalid ptr-to-ptr casts with trait objects

This is a follow-up to rust-lang/rust#120248 to improve some of its error messages.

1. Make the borrowcheck error for "type annotation requires that x must outlive y" actually point at the type annotation, i.e. the type `T` in a `x as T` cast. This makes the error more consistent with other errors caused by type annotation in other places, such as
```text
error: lifetime may not live long enough
 --> src/lib.rs:4:12
  |
3 | fn bar(a: &i32) {
  |           - let's call the lifetime of this reference `'1`
4 |     let b: &'static i32 = a;
  |            ^^^^^^^^^^^^ type annotation requires that `'1` must outlive `'static`
```

2. Don't say "cast" when we actually mean "coercion" and give borrowcheck errors from actual casts (which is currently just the check added in rust-lang/rust#120248) a higher priority than ones from coercions. This can improve the errors for ptr-to-ptr cast between trait objects because they are are lowered as an upcast "unsizing" coercion if possible (which may be the identity upcast) followed by the actual cast.

3. Bring back the old "casting X as Y is invalid" message for type mismatch in the principals and reword the "vtable kinds may not match" message to more accurately describe the pointer metadata and not refer to "vtables" if the metadata is unknown.

fixes rust-lang/rust#130030

r? `@WaffleLapkin` but feel free to reassign