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Check if enum from foreign crate has any non exhaustive variants when attempting a cast #92744

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lambinoo
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@lambinoo lambinoo commented Jan 10, 2022

Fixes #91161

As stated in the issue, this will require a crater run as it might break other people's stuff.

@rustbot rustbot added the T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. label Jan 10, 2022
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r? @jackh726

(rust-highfive has picked a reviewer for you, use r? to override)

@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jan 10, 2022
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camelid commented Jan 10, 2022

Is this PR supposed to close the related issue? If so, please put Fixes #NNNN. in the PR description instead of "Related issue".

@lambinoo lambinoo force-pushed the I-91161-non-exhaustive-foreign-variants branch 2 times, most recently from 153f5b5 to e40df26 Compare January 11, 2022 06:25
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@lambinoo lambinoo force-pushed the I-91161-non-exhaustive-foreign-variants branch from e40df26 to 3072937 Compare January 11, 2022 06:42
@lambinoo lambinoo force-pushed the I-91161-non-exhaustive-foreign-variants branch 2 times, most recently from a6284cc to db10284 Compare January 11, 2022 20:25
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@craterbot check

Let's get this in the queue.

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🚨 Error: missing start toolchain

🆘 If you have any trouble with Crater please ping @rust-lang/infra!
ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

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Ah right

@bors try

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bors commented Jan 11, 2022

⌛ Trying commit db10284f8875c5e787cb692a343dad4621a54dd0 with merge 2932526cb1d50a7e0c62268bc29edbc68b754cb2...

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bors commented Jan 11, 2022

☀️ Try build successful - checks-actions
Build commit: 2932526cb1d50a7e0c62268bc29edbc68b754cb2 (2932526cb1d50a7e0c62268bc29edbc68b754cb2)

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camelid commented Jan 11, 2022

@craterbot check

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👌 Experiment pr-92744 created and queued.
🤖 Automatically detected try build 2932526cb1d50a7e0c62268bc29edbc68b754cb2
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

@craterbot craterbot added S-waiting-on-crater Status: Waiting on a crater run to be completed. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jan 11, 2022
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camelid commented Jan 11, 2022

Will craterbot's check mode run check --all-targets (i.e., tests too)? Shouldn't be a huge difference, but wanted to bring it up.

@lambinoo lambinoo force-pushed the I-91161-non-exhaustive-foreign-variants branch 4 times, most recently from e776465 to db10284 Compare January 12, 2022 16:49
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Don't mind those pushes... working from too many terminals while being very tired is a bad bad idea..

@lambinoo lambinoo force-pushed the I-91161-non-exhaustive-foreign-variants branch from 2932526 to db10284 Compare January 13, 2022 20:37
@Mark-Simulacrum Mark-Simulacrum removed the I-lang-nominated The issue / PR has been nominated for discussion during a lang team meeting. label Feb 8, 2022
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@rfcbot reviewed

@rfcbot rfcbot added finished-final-comment-period The final comment period is finished for this PR / Issue. and removed final-comment-period In the final comment period and will be merged soon unless new substantive objections are raised. labels Feb 18, 2022
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rfcbot commented Feb 18, 2022

The final comment period, with a disposition to merge, as per the review above, is now complete.

As the automated representative of the governance process, I would like to thank the author for their work and everyone else who contributed.

This will be merged soon.

@rfcbot rfcbot added the to-announce Announce this issue on triage meeting label Feb 18, 2022
@apiraino apiraino removed the to-announce Announce this issue on triage meeting label Mar 3, 2022
@scottmcm scottmcm force-pushed the I-91161-non-exhaustive-foreign-variants branch from db10284 to dfb3713 Compare August 10, 2022 17:08
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Sorry that we accidentally let this languish for so long. I've rebased to fix the conflicts; let me check that CI is still happy.

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With the FCP complete and the crater results clean, I think this is good to go. Thanks for the PR!

@bors r+

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bors commented Aug 10, 2022

📌 Commit dfb3713 has been approved by scottmcm

It is now in the queue for this repository.

@bors bors 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-team Status: Awaiting decision from the relevant subteam (see the T-<team> label). labels Aug 10, 2022
Dylan-DPC added a commit to Dylan-DPC/rust that referenced this pull request Aug 11, 2022
…eign-variants, r=scottmcm

Check if enum from foreign crate has any non exhaustive variants when attempting a cast

Fixes rust-lang#91161

As stated in the issue, this will require a crater run as it might break other people's stuff.
bors added a commit to rust-lang-ci/rust that referenced this pull request Aug 11, 2022
Rollup of 11 pull requests

Successful merges:

 - rust-lang#92744 (Check if enum from foreign crate has any non exhaustive variants when attempting a cast)
 - rust-lang#99110 (Determine match_has_guard from candidates instead of looking up thir table again)
 - rust-lang#100184 (Stabilize ptr_const_cast)
 - rust-lang#100192 ( Remove duplicated temporaries creating during box derefs elaboration)
 - rust-lang#100232 (Do not consider method call receiver as an argument in AST.)
 - rust-lang#100287 (linux: Use `pthread_setname_np` instead of `prctl`)
 - rust-lang#100351 (Use `&mut Diagnostic` instead of `&mut DiagnosticBuilder` unless needed)
 - rust-lang#100370 (Remove more Clean trait implementations)
 - rust-lang#100391 (Improve size assertions)
 - rust-lang#100398 (Improve `-Zhir-stats`)
 - rust-lang#100403 (Improve error messages when running rustdoc GUI tests)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit dfddc2f into rust-lang:master Aug 11, 2022
@rustbot rustbot added this to the 1.65.0 milestone Aug 11, 2022
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ehuss commented Aug 13, 2022

@lambinoo Would you be willing to post a PR to the reference to add this restriction to the #[non_exhaustive] docs? I was thinking just adding another sentence towards the bottom explaining the limitation on as casting and show an example similar to the other examples.

bors added a commit to rust-lang-ci/rust that referenced this pull request Sep 2, 2022
Rollup of 7 pull requests

Successful merges:

 - rust-lang#92744 (Check if enum from foreign crate has any non exhaustive variants when attempting a cast)
 - rust-lang#99337 (rustdoc: simplify highlight.rs)
 - rust-lang#100007 (Never inline Windows dtor access)
 - rust-lang#100030 (cleanup code w/ pointers in std a little)
 - rust-lang#100192 ( Remove duplicated temporaries creating during box derefs elaboration)
 - rust-lang#100247 (Generalize trait object generic param check to aliases.)
 - rust-lang#100374 (Improve crate selection on rustdoc search results page)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
wip-sync pushed a commit to NetBSD/pkgsrc-wip that referenced this pull request Nov 27, 2022
Pkgsrc changes:
 * We now manage to build for mipsel-unknown-netbsd, but despite the
   target spec saying cpu = "mips3", the compiler manages to emit 64-bit
   instructions which cause "illegal instruction" error.  Will need more
   work.  The mipsel-unknown-netbsd entry is commentd out since there
   is no 1.64.0 bootstrap.
 * Managed to retain the build of aarch64_be, llvm needed a patch to
   avoid use of neon instructions in the BE case (llvm doesn't support
   use of neon in BE mode).  Ref. patch to
   src/llvm-project/llvm/lib/Support/BLAKE3/blake3_impl.h.
 * The minimum gcc version is now 7.x, and that includes the cross-compiler
   for the targets.  For i386 this also needs to /usr/include/gcc-7 include
   files in the target root, because immintrin.h from gcc 5 is not
   compatible with gcc 7.x.  This applies for the targets where we build
   against a root from netbsd-8 (sparc64, powerpc, i386), and files/gcc-wrap
   gets a hack for this.
 * Pick up tweak for -latomic inclusion from
   rust-lang/rust#104220
   and
   rust-lang/rust#104572
 * Retain ability to do 32-bit NetBSD, by changing from 64 to 32 bit
   types in library/std/src/sys/unix/thread_parker/netbsd.rs.
 * I've struggled a bit to get the "openssl-src" build with -latomic
   where it's needed.  I introduce "NetBSD-generic32" system type and
   use it for the NetBSD mipsel target.  There is another attempt to
   do the same in the patch to vendor/openssl-sys/build/main.rs.
 * Bump bootstraps to 1.64.0, checksum updates.

Upstream changes:

Version 1.65.0 (2022-11-03)
==========================

Language
--------
- [Error on `as` casts of enums with `#[non_exhaustive]` variants]
  (rust-lang/rust#92744)
- [Stabilize `let else`](rust-lang/rust#93628)
- [Stabilize generic associated types (GATs)]
  (rust-lang/rust#96709)
- [Add lints `let_underscore_drop`, `let_underscore_lock`, and
  `let_underscore_must_use` from Clippy]
  (rust-lang/rust#97739)
- [Stabilize `break`ing from arbitrary labeled blocks ("label-break-value")]
  (rust-lang/rust#99332)
- [Uninitialized integers, floats, and raw pointers are now considered
  immediate UB](rust-lang/rust#98919).
  Usage of `MaybeUninit` is the correct way to work with uninitialized
  memory.
- [Stabilize raw-dylib for Windows x86_64, aarch64, and thumbv7a]
  (rust-lang/rust#99916)
- [Do not allow `Drop` impl on foreign ADTs]
  (rust-lang/rust#99576)

Compiler
--------
- [Stabilize -Csplit-debuginfo on Linux]
  (rust-lang/rust#98051)
- [Use niche-filling optimization even when multiple variants have
  data] (rust-lang/rust#94075)
- [Associated type projections are now verified to be well-formed
  prior to resolving the underlying type]
  (rust-lang/rust#99217)
- [Stringify non-shorthand visibility correctly]
  (rust-lang/rust#100350)
- [Normalize struct field types when unsizing]
  (rust-lang/rust#101831)
- [Update to LLVM 15](rust-lang/rust#99464)
- [Fix aarch64 call abi to correctly zeroext when needed]
  (rust-lang/rust#97800)
- [debuginfo: Generalize C++-like encoding for enums]
  (rust-lang/rust#98393)
- [Add `special_module_name` lint]
  (rust-lang/rust#94467)
- [Add support for generating unique profraw files by default when
  using `-C instrument-coverage`]
  (rust-lang/rust#100384)
- [Allow dynamic linking for iOS/tvOS targets]
  (rust-lang/rust#100636)

New targets:
- [Add armv4t-none-eabi as a tier 3 target]
  (rust-lang/rust#100244)
- [Add powerpc64-unknown-openbsd and riscv64-unknown-openbsd as tier 3 targets]
  (rust-lang/rust#101025)
- Refer to Rust's [platform support page][platform-support-doc] for more
  information on Rust's tiered platform support.

Libraries
---------
- [Don't generate `PartialEq::ne` in derive(PartialEq)]
  (rust-lang/rust#98655)
- [Windows RNG: Use `BCRYPT_RNG_ALG_HANDLE` by default]
  (rust-lang/rust#101325)
- [Forbid mixing `System` with direct system allocator calls]
  (rust-lang/rust#101394)
- [Document no support for writing to non-blocking stdio/stderr]
  (rust-lang/rust#101416)
- [`std::layout::Layout` size must not overflow `isize::MAX` when
  rounded up to `align`](rust-lang/rust#95295)
  This also changes the safety conditions on
  `Layout::from_size_align_unchecked`.

Stabilized APIs
---------------
- [`std::backtrace::Backtrace`]
  (https://doc.rust-lang.org/stable/std/backtrace/struct.Backtrace.html)
- [`Bound::as_ref`]
  (https://doc.rust-lang.org/stable/std/ops/enum.Bound.html#method.as_ref)
- [`std::io::read_to_string`]
  (https://doc.rust-lang.org/stable/std/io/fn.read_to_string.html)
- [`<*const T>::cast_mut`]
  (https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.cast_mut)
- [`<*mut T>::cast_const`]
  (https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.cast_const)

These APIs are now stable in const contexts:
- [`<*const T>::offset_from`]
  (https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.offset_from)
- [`<*mut T>::offset_from`]
  (https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.offset_from)

Cargo
-----
- [Apply GitHub fast path even for partial hashes]
  (rust-lang/cargo#10807)
- [Do not add home bin path to PATH if it's already there]
  (rust-lang/cargo#11023)
- [Take priority into account within the pending queue]
  (rust-lang/cargo#11032).
  This slightly optimizes job scheduling by Cargo, with typically
  small improvements on larger crate graph builds.

Compatibility Notes
-------------------
- [`std::layout::Layout` size must not overflow `isize::MAX` when
  rounded up to `align`] (rust-lang/rust#95295).
  This also changes the safety conditions on
  `Layout::from_size_align_unchecked`.
- [`PollFn` now only implements `Unpin` if the closure is `Unpin`]
  (rust-lang/rust#102737).
  This is a possible breaking change if users were relying on the
  blanket unpin implementation.  See discussion on the PR for
  details of why this change was made.
- [Drop ExactSizeIterator impl from std::char::EscapeAscii]
  (rust-lang/rust#99880)
  This is a backwards-incompatible change to the standard library's
  surface area, but is unlikely to affect real world usage.
- [Do not consider a single repeated lifetime eligible for elision
  in the return type] (rust-lang/rust#103450)
  This behavior was unintentionally changed in 1.64.0, and this
  release reverts that change by making this an error again.
- [Reenable disabled early syntax gates as future-incompatibility
  lints] (rust-lang/rust#99935)
- [Update the minimum external LLVM to 13]
  (rust-lang/rust#100460)
- [Don't duplicate file descriptors into stdio fds]
  (rust-lang/rust#101426)
- [Sunset RLS](rust-lang/rust#100863)
- [Deny usage of `#![cfg_attr(..., crate_type = ...)]` to set the
  crate type] (rust-lang/rust#99784)
  This strengthens the forward compatibility lint
  deprecated_cfg_attr_crate_type_name to deny.
- [`llvm-has-rust-patches` allows setting the build system to treat
  the LLVM as having Rust-specific patches]
  (rust-lang/rust#101072)
  This option may need to be set for distributions that are building
  Rust with a patched LLVM via `llvm-config`, not the built-in
  LLVM.

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 `x.sh` and `x.ps1` shell scripts]
  (rust-lang/rust#99992)
- [compiletest: use target cfg instead of hard-coded tables]
  (rust-lang/rust#100260)
- [Use object instead of LLVM for reading bitcode from rlibs]
  (rust-lang/rust#98100)
- [Enable MIR inlining for optimized compilations]
  (rust-lang/rust#91743)
  This provides a 3-10% improvement in compiletimes for real world
  crates. See [perf results]
  (https://perf.rust-lang.org/compare.html?start=aedf78e56b2279cc869962feac5153b6ba7001ed&end=0075bb4fad68e64b6d1be06bf2db366c30bc75e1&stat=instructions:u).
netbsd-srcmastr pushed a commit to NetBSD/pkgsrc that referenced this pull request Jan 23, 2023
Pkgsrc changes:
 * pkglint cleanups, bump bootstrap kits to 1.65.0.
 * New target: mipsel-unknown-netbsd, for cpu=mips32 with soft-float.
 * Managed to retain the build of aarch64_be, llvm needed a patch to
   avoid use of neon instructions in the BE case (llvm doesn't support
   use of neon in BE mode).  Ref. patch to
   src/llvm-project/llvm/lib/Support/BLAKE3/blake3_impl.h.
   Also submitted upstream of LLVM to the BLAKE3 maintainers.
 * The minimum gcc version is now 7.x, and that includes the
   cross-compiler for the targets.  For i386 this also needs to
   /usr/include/gcc-7 include files in the target root, because
   immintrin.h from gcc 5 is not compatible with gcc 7.x.  This
   applies for the targets where we build against a root from netbsd-8
   (sparc64, powerpc, i386), and files/gcc-wrap gets a hack for this.
 * Pick up tweak for -latomic inclusion from
   rust-lang/rust#104220
   and
   rust-lang/rust#104572
 * Retain ability to do 32-bit NetBSD, by changing from 64 to 32 bit
   types in library/std/src/sys/unix/thread_parker/netbsd.rs.
 * I've tried to get the "openssl-src" build with -latomic where it's
   needed.  I've introduced the "NetBSD-generic32" system type and use
   it for the NetBSD mipsel target.  There is another attempt to do
   the same in the patch to vendor/openssl-sys/build/main.rs.


Upstream changes:

Version 1.66.1 (2023-01-10)
===========================

- Added validation of SSH host keys for git URLs in Cargo
  ([CVE-2022-46176](https://www.cve.org/CVERecord?id=CVE-2022-46176))


Version 1.66.0 (2022-12-15)
===========================

Language
--------
- [Permit specifying explicit discriminants on all `repr(Int)`
  enums](rust-lang/rust#95710)
  ```rust
  #[repr(u8)]
  enum Foo {
      A(u8) = 0,
      B(i8) = 1,
      C(bool) = 42,
  }
  ```
- [Allow transmutes between the same type differing only in
  lifetimes](rust-lang/rust#101520)
- [Change constant evaluation errors from a deny-by-default lint to a
  hard error](rust-lang/rust#102091)
- [Trigger `must_use` on `impl Trait` for
  supertraits](rust-lang/rust#102287) This
  makes `impl ExactSizeIterator` respect the existing `#[must_use]`
  annotation on `Iterator`.
- [Allow `..X` and `..=X` in
  patterns](rust-lang/rust#102275)
- [Uplift `clippy::for_loops_over_fallibles` lint into
  rustc](rust-lang/rust#99696)
- [Stabilize `sym` operands in inline
  assembly](rust-lang/rust#103168)
- [Update to Unicode 15](rust-lang/rust#101912)
- [Opaque types no longer imply lifetime
  bounds](rust-lang/rust#95474) This is a
  soundness fix which may break code that was erroneously relying on this
  behavior.

Compiler
--------
- [Add armv5te-none-eabi and thumbv5te-none-eabi tier 3
  targets](rust-lang/rust#101329)
  - Refer to Rust's [platform support page][platform-support-doc] for
    more information on Rust's tiered platform support.
- [Add support for linking against macOS universal
  libraries](rust-lang/rust#98736)

Libraries
---------
- [Fix `#[derive(Default)]` on a generic `#[default]` enum adding
  unnecessary `Default`
  bounds](rust-lang/rust#101040)
- [Update to Unicode 15](rust-lang/rust#101821)

Stabilized APIs
---------------
- [`proc_macro::Span::source_text`](https://doc.rust-lang.org/stable/proc_macro/struct.Span.html#method.source_text)
- [`uX::{checked_add_signed, overflowing_add_signed,
  saturating_add_signed,
  wrapping_add_signed}`](https://doc.rust-lang.org/stable/std/primitive.u8.html#method.checked_add_signed)
- [`iX::{checked_add_unsigned, overflowing_add_unsigned,
  saturating_add_unsigned,
  wrapping_add_unsigned}`](https://doc.rust-lang.org/stable/std/primitive.i8.html#method.checked_add_unsigned)
- [`iX::{checked_sub_unsigned, overflowing_sub_unsigned,
  saturating_sub_unsigned,
  wrapping_sub_unsigned}`](https://doc.rust-lang.org/stable/std/primitive.i8.html#method.checked_sub_unsigned)
- [`BTreeSet::{first, last, pop_first,
  pop_last}`](https://doc.rust-lang.org/stable/std/collections/struct.BTreeSet.html#method.first)
- [`BTreeMap::{first_key_value, last_key_value, first_entry, last_entry,
  pop_first,
  pop_last}`](https://doc.rust-lang.org/stable/std/collections/struct.BTreeMap.html#method.first_key_value)
- [Add `AsFd` implementations for stdio lock types on
  WASI.](rust-lang/rust#101768)
- [`impl TryFrom<Vec<T>> for Box<[T;
  N]>`](https://doc.rust-lang.org/stable/std/boxed/struct.Box.html#impl-TryFrom%3CVec%3CT%2C%20Global%3E%3E-for-Box%3C%5BT%3B%20N%5D%2C%20Global%3E)
- [`core::hint::black_box`](https://doc.rust-lang.org/stable/std/hint/fn.black_box.html)
- [`Duration::try_from_secs_{f32,f64}`](https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.try_from_secs_f32)
- [`Option::unzip`](https://doc.rust-lang.org/stable/std/option/enum.Option.html#method.unzip)
- [`std::os::fd`](https://doc.rust-lang.org/stable/std/os/fd/index.html)

Rustdoc
-------
- [Add Rustdoc warning for invalid HTML tags in the
  documentation](rust-lang/rust#101720)

Cargo
-----
- [Added `cargo remove` to remove dependencies from
  Cargo.toml](https://doc.rust-lang.org/nightly/cargo/commands/cargo-remove.html)
- [`cargo publish` now waits for the new version to be downloadable
  before exiting](rust-lang/cargo#11062)

See [detailed release notes](https://github.com/rust-lang/cargo/blob/master/CHANGELOG.md#cargo-166-2022-12-15) for more.

Compatibility Notes
-------------------
- [Only apply `ProceduralMasquerade` hack to older versions of
  `rental`](rust-lang/rust#94063)
- [Don't export `__heap_base` and `__data_end` on
  wasm32-wasi.](rust-lang/rust#102385)
- [Don't export `__wasm_init_memory` on
  WebAssembly.](rust-lang/rust#102426)
- [Only export `__tls_*` on
  wasm32-unknown-unknown.](rust-lang/rust#102440)
- [Don't link to `libresolv` in libstd on
  Darwin](rust-lang/rust#102766)
- [Update libstd's libc to 0.2.135 (to make `libstd` no longer pull in
  `libiconv.dylib` on
  Darwin)](rust-lang/rust#103277)
- [Opaque types no longer imply lifetime
  bounds](rust-lang/rust#95474)
  This is a soundness fix which may break code that was erroneously
  relying on this behavior.
- [Make `order_dependent_trait_objects` show up in future-breakage
  reports](rust-lang/rust#102635)
- [Change std::process::Command spawning to default to inheriting the
  parent's signal mask](rust-lang/rust#101077)

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.

- [Enable BOLT for LLVM
  compilation](rust-lang/rust#94381)
- [Enable LTO for
  rustc_driver.so](rust-lang/rust#101403)


Version 1.65.0 (2022-11-03)
==========================

Language
--------
- [Error on `as` casts of enums with `#[non_exhaustive]` variants]
  (rust-lang/rust#92744)
- [Stabilize `let else`](rust-lang/rust#93628)
- [Stabilize generic associated types (GATs)]
  (rust-lang/rust#96709)
- [Add lints `let_underscore_drop`, `let_underscore_lock`, and
  `let_underscore_must_use` from Clippy]
  (rust-lang/rust#97739)
- [Stabilize `break`ing from arbitrary labeled blocks ("label-break-value")]
  (rust-lang/rust#99332)
- [Uninitialized integers, floats, and raw pointers are now considered
  immediate UB](rust-lang/rust#98919).
  Usage of `MaybeUninit` is the correct way to work with uninitialized
  memory.
- [Stabilize raw-dylib for Windows x86_64, aarch64, and thumbv7a]
  (rust-lang/rust#99916)
- [Do not allow `Drop` impl on foreign ADTs]
  (rust-lang/rust#99576)

Compiler
--------
- [Stabilize -Csplit-debuginfo on Linux]
  (rust-lang/rust#98051)
- [Use niche-filling optimization even when multiple variants have
  data] (rust-lang/rust#94075)
- [Associated type projections are now verified to be well-formed
  prior to resolving the underlying type]
  (rust-lang/rust#99217)
- [Stringify non-shorthand visibility correctly]
  (rust-lang/rust#100350)
- [Normalize struct field types when unsizing]
  (rust-lang/rust#101831)
- [Update to LLVM 15](rust-lang/rust#99464)
- [Fix aarch64 call abi to correctly zeroext when needed]
  (rust-lang/rust#97800)
- [debuginfo: Generalize C++-like encoding for enums]
  (rust-lang/rust#98393)
- [Add `special_module_name` lint]
  (rust-lang/rust#94467)
- [Add support for generating unique profraw files by default when
  using `-C instrument-coverage`]
  (rust-lang/rust#100384)
- [Allow dynamic linking for iOS/tvOS targets]
  (rust-lang/rust#100636)

New targets:
- [Add armv4t-none-eabi as a tier 3 target]
  (rust-lang/rust#100244)
- [Add powerpc64-unknown-openbsd and riscv64-unknown-openbsd as tier 3 targets]
  (rust-lang/rust#101025)
- Refer to Rust's [platform support page][platform-support-doc] for more
  information on Rust's tiered platform support.

Libraries
---------
- [Don't generate `PartialEq::ne` in derive(PartialEq)]
  (rust-lang/rust#98655)
- [Windows RNG: Use `BCRYPT_RNG_ALG_HANDLE` by default]
  (rust-lang/rust#101325)
- [Forbid mixing `System` with direct system allocator calls]
  (rust-lang/rust#101394)
- [Document no support for writing to non-blocking stdio/stderr]
  (rust-lang/rust#101416)
- [`std::layout::Layout` size must not overflow `isize::MAX` when
  rounded up to `align`](rust-lang/rust#95295)
  This also changes the safety conditions on
  `Layout::from_size_align_unchecked`.

Stabilized APIs
---------------
- [`std::backtrace::Backtrace`]
  (https://doc.rust-lang.org/stable/std/backtrace/struct.Backtrace.html)
- [`Bound::as_ref`]
  (https://doc.rust-lang.org/stable/std/ops/enum.Bound.html#method.as_ref)
- [`std::io::read_to_string`]
  (https://doc.rust-lang.org/stable/std/io/fn.read_to_string.html)
- [`<*const T>::cast_mut`]
  (https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.cast_mut)
- [`<*mut T>::cast_const`]
  (https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.cast_const)

These APIs are now stable in const contexts:
- [`<*const T>::offset_from`]
  (https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.offset_from)
- [`<*mut T>::offset_from`]
  (https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.offset_from)

Cargo
-----
- [Apply GitHub fast path even for partial hashes]
  (rust-lang/cargo#10807)
- [Do not add home bin path to PATH if it's already there]
  (rust-lang/cargo#11023)
- [Take priority into account within the pending queue]
  (rust-lang/cargo#11032).
  This slightly optimizes job scheduling by Cargo, with typically
  small improvements on larger crate graph builds.

Compatibility Notes
-------------------
- [`std::layout::Layout` size must not overflow `isize::MAX` when
  rounded up to `align`] (rust-lang/rust#95295).
  This also changes the safety conditions on
  `Layout::from_size_align_unchecked`.
- [`PollFn` now only implements `Unpin` if the closure is `Unpin`]
  (rust-lang/rust#102737).
  This is a possible breaking change if users were relying on the
  blanket unpin implementation.  See discussion on the PR for
  details of why this change was made.
- [Drop ExactSizeIterator impl from std::char::EscapeAscii]
  (rust-lang/rust#99880)
  This is a backwards-incompatible change to the standard library's
  surface area, but is unlikely to affect real world usage.
- [Do not consider a single repeated lifetime eligible for elision
  in the return type] (rust-lang/rust#103450)
  This behavior was unintentionally changed in 1.64.0, and this
  release reverts that change by making this an error again.
- [Reenable disabled early syntax gates as future-incompatibility
  lints] (rust-lang/rust#99935)
- [Update the minimum external LLVM to 13]
  (rust-lang/rust#100460)
- [Don't duplicate file descriptors into stdio fds]
  (rust-lang/rust#101426)
- [Sunset RLS](rust-lang/rust#100863)
- [Deny usage of `#![cfg_attr(..., crate_type = ...)]` to set the
  crate type] (rust-lang/rust#99784)
  This strengthens the forward compatibility lint
  deprecated_cfg_attr_crate_type_name to deny.
- [`llvm-has-rust-patches` allows setting the build system to treat
  the LLVM as having Rust-specific patches]
  (rust-lang/rust#101072)
  This option may need to be set for distributions that are building
  Rust with a patched LLVM via `llvm-config`, not the built-in
  LLVM.

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 `x.sh` and `x.ps1` shell scripts]
  (rust-lang/rust#99992)
- [compiletest: use target cfg instead of hard-coded tables]
  (rust-lang/rust#100260)
- [Use object instead of LLVM for reading bitcode from rlibs]
  (rust-lang/rust#98100)
- [Enable MIR inlining for optimized compilations]
  (rust-lang/rust#91743)
  This provides a 3-10% improvement in compiletimes for real world
  crates. See [perf results]
  (https://perf.rust-lang.org/compare.html?start=aedf78e56b2279cc869962feac5153b6ba7001ed&end=0075bb4fad68e64b6d1be06bf2db366c30bc75e1&stat=instructions:u).
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#[non_exhaustive] on variant should block cross-crate as casts