rework winnowing to sensibly handle global where-bounds

this is somewhat weird, but it at least allows us to mirror this behavior in the new solver:
- trivial builtin-impls
- non-global where-bounds, bailing with ambiguity if at least one global where-bound exists
- object ☠️ + alias-bound candidates
- merge candidates ignoring global where-bounds

This is a different approach from rust-lang#124592 which maintains the "if there are global where-bounds, don't guide type inference using non-global where-bounds" behavior, hopefully avoiding the breakage and means we use guidance from non-global where-bounds in fewer, instead of in more cases.

r? `@compiler-errors`

…errors

-Znext-solver: modify candidate preference rules

This implements the design proposed in the FCP in rust-lang#132325 and matches the old solver behavior. I hope the inline comments are all sufficiently clear, I personally think this is a fairly clear improvement over the existing approach using `fn discard_impls_shadowed_by_env`. This fixes rust-lang/trait-system-refactor-initiative#96.

This also fixes rust-lang#133639 which encounters an ICE in negative coherence when evaluating the where-clause. Given the features required to trigger this ICE 🤷

r? `@compiler-errors`

…errors

-Znext-solver: modify candidate preference rules

This implements the design proposed in the FCP in rust-lang#132325 and matches the old solver behavior. I hope the inline comments are all sufficiently clear, I personally think this is a fairly clear improvement over the existing approach using `fn discard_impls_shadowed_by_env`. This fixes rust-lang/trait-system-refactor-initiative#96.

This also fixes rust-lang#133639 which encounters an ICE in negative coherence when evaluating the where-clause. Given the features required to trigger this ICE 🤷

r? ``@compiler-errors``

Rollup merge of rust-lang#133643 - lcnr:merge-candidates, r=compiler-errors

-Znext-solver: modify candidate preference rules

This implements the design proposed in the FCP in rust-lang#132325 and matches the old solver behavior. I hope the inline comments are all sufficiently clear, I personally think this is a fairly clear improvement over the existing approach using `fn discard_impls_shadowed_by_env`. This fixes rust-lang/trait-system-refactor-initiative#96.

This also fixes rust-lang#133639 which encounters an ICE in negative coherence when evaluating the where-clause. Given the features required to trigger this ICE 🤷

r? ``@compiler-errors``

Pkgsrc changes relative to rust184:

 * patch reorganization to deal with new version
   of upstream vendored crates, checksum updates.

Version 1.85.0 (2025-02-20)
==========================

Language
--------
- [The 2024 Edition is now stable.]
  (rust-lang/rust#133349)
  See [the edition guide]
  (https://doc.rust-lang.org/nightly/edition-guide/rust-2024/index.html)
  for more details.
- [Stabilize async closures]
  (rust-lang/rust#132706)
  See [RFC 3668]
  (https://rust-lang.github.io/rfcs/3668-async-closures.html) for more details.
- [Stabilize `#[diagnostic::do_not_recommend]`]
  (rust-lang/rust#132056)
- [Add `unpredictable_function_pointer_comparisons` lint to warn
  against function pointer comparisons]
  (rust-lang/rust#118833)
- [Lint on combining `#[no_mangle]` and `#[export_name]` attributes.]
  (rust-lang/rust#131558)

Compiler
--------
- [The unstable flag `-Zpolymorphize` has been removed]
  (rust-lang/rust#133883), see
  rust-lang/compiler-team#810 for some
  background.

Platform Support
----------------
- [Promote `powerpc64le-unknown-linux-musl` to tier 2 with host tools]
  (rust-lang/rust#133801)

Refer to Rust's [platform support page][platform-support-doc]
for more information on Rust's tiered platform support.

Libraries
---------
- [Panics in the standard library now have a leading `library/` in their path]
  (rust-lang/rust#132390)
- [`std::env::home_dir()` on Windows now ignores the non-standard
  `$HOME` environment variable]
  (rust-lang/rust#132515)

  It will be un-deprecated in a subsequent release.
- [Add `AsyncFn*` to the prelude in all editions.]
  (rust-lang/rust#132611)

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

- [`BuildHasherDefault::new`]
  (https://doc.rust-lang.org/stable/std/hash/struct.BuildHasherDefault.html#method.new)
- [`ptr::fn_addr_eq`]
  (https://doc.rust-lang.org/std/ptr/fn.fn_addr_eq.html)
- [`io::ErrorKind::QuotaExceeded`]
  (https://doc.rust-lang.org/stable/std/io/enum.ErrorKind.html#variant.QuotaExceeded)
- [`io::ErrorKind::CrossesDevices`]
  (https://doc.rust-lang.org/stable/std/io/enum.ErrorKind.html#variant.CrossesDevices)
- [`{float}::midpoint`]
  (https://doc.rust-lang.org/core/primitive.f32.html#method.midpoint)
- [Unsigned `{integer}::midpoint`]
  (https://doc.rust-lang.org/std/primitive.u64.html#method.midpoint)
- [`NonZeroU*::midpoint`]
  (https://doc.rust-lang.org/std/num/type.NonZeroU32.html#method.midpoint)
- [impl `std::iter::Extend` for tuples with arity 1 through 12]
  (https://doc.rust-lang.org/stable/std/iter/trait.Extend.html#impl-Extend%3C(A,)%3E-for-(EA,))
- [`FromIterator<(A, ...)>` for tuples with arity 1 through 12]
  (https://doc.rust-lang.org/stable/std/iter/trait.FromIterator.html#impl-FromIterator%3C(EA,)%3E-for-(A,))
- [`std::task::Waker::noop`]
  (https://doc.rust-lang.org/stable/std/task/struct.Waker.html#method.noop)

These APIs are now stable in const contexts:

- [`mem::size_of_val`]
  (https://doc.rust-lang.org/stable/std/mem/fn.size_of_val.html)
- [`mem::align_of_val`]
  (https://doc.rust-lang.org/stable/std/mem/fn.align_of_val.html)
- [`Layout::for_value`]
  (https://doc.rust-lang.org/stable/std/alloc/struct.Layout.html#method.for_value)
- [`Layout::align_to`]
  (https://doc.rust-lang.org/stable/std/alloc/struct.Layout.html#method.align_to)
- [`Layout::pad_to_align`]
  (https://doc.rust-lang.org/stable/std/alloc/struct.Layout.html#method.pad_to_align)
- [`Layout::extend`]
  (https://doc.rust-lang.org/stable/std/alloc/struct.Layout.html#method.extend)
- [`Layout::array`]
  (https://doc.rust-lang.org/stable/std/alloc/struct.Layout.html#method.array)
- [`std::mem::swap`]
  (https://doc.rust-lang.org/stable/std/mem/fn.swap.html)
- [`std::ptr::swap`]
  (https://doc.rust-lang.org/stable/std/ptr/fn.swap.html)
- [`NonNull::new`]
  (https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.new)
- [`HashMap::with_hasher`]
  (https://doc.rust-lang.org/stable/std/collections/struct.HashMap.html#method.with_hasher)
- [`HashSet::with_hasher`]
  (https://doc.rust-lang.org/stable/std/collections/struct.HashSet.html#method.with_hasher)
- [`BuildHasherDefault::new`]
  (https://doc.rust-lang.org/stable/std/hash/struct.BuildHasherDefault.html#method.new)
- [`<float>::recip`]
  (https://doc.rust-lang.org/stable/std/primitive.f32.html#method.recip)
- [`<float>::to_degrees`]
  (https://doc.rust-lang.org/stable/std/primitive.f32.html#method.to_degrees)
- [`<float>::to_radians`]
  (https://doc.rust-lang.org/stable/std/primitive.f32.html#method.to_radians)
- [`<float>::max`]
  (https://doc.rust-lang.org/stable/std/primitive.f32.html#method.max)
- [`<float>::min`]
  (https://doc.rust-lang.org/stable/std/primitive.f32.html#method.min)
- [`<float>::clamp`]
  (https://doc.rust-lang.org/stable/std/primitive.f32.html#method.clamp)
- [`<float>::abs`]
  (https://doc.rust-lang.org/stable/std/primitive.f32.html#method.abs)
- [`<float>::signum`]
  (https://doc.rust-lang.org/stable/std/primitive.f32.html#method.signum)
- [`<float>::copysign`]
  (https://doc.rust-lang.org/stable/std/primitive.f32.html#method.copysign)
- [`MaybeUninit::write`]
  (https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.write)

Cargo
-----
- [Add future-incompatibility warning against keywords in cfgs and
  add raw-idents] (rust-lang/cargo#14671)
- [Stabilize higher precedence trailing flags]
  (rust-lang/cargo#14900)
- [Pass `CARGO_CFG_FEATURE` to build scripts]
  (rust-lang/cargo#14902)

Rustdoc
-----
- [Doc comment on impl blocks shows the first line, even when the
  impl block is collapsed] (rust-lang/rust#132155)

Compatibility Notes
-------------------
- [`rustc` no longer treats the `test` cfg as a well known
  check-cfg] (rust-lang/rust#131729),
  instead it is up to the build systems and users of
  `--check-cfg`[^check-cfg] to set it as a well known cfg using
  `--check-cfg=cfg(test)`.

  This is done to enable build systems like Cargo to set it
  conditionally, as not all source files are suitable for unit
  tests.

  [Cargo (for now) unconditionally sets the `test` cfg as a well known cfg]
  (rust-lang/cargo#14963).
  [^check-cfg]: https://doc.rust-lang.org/nightly/rustc/check-cfg.html

- [Disable potentially incorrect type inference if there are trivial
  and non-trivial where-clauses]
  (rust-lang/rust#132325)

- `std::env::home_dir()` has been deprecated for years, because it
  can give surprising results in some Windows configurations if the
  `HOME` environment variable is set (which is not the normal
  configuration on Windows). We had previously avoided changing its
  behavior, out of concern for compatibility with code depending on
  this non-standard configuration. Given how long this function has
  been deprecated, we're now fixing its behavior as a bugfix. A
  subsequent release will remove the deprecation for this function.

- [Make `core::ffi::c_char` signedness more closely match that of
  the platform-default `char`]
  (rust-lang/rust#132975)

  This changed `c_char` from an `i8` to `u8` or vice versa on many
  Tier 2 and 3 targets (mostly Arm and RISC-V embedded targets).
  The new definition may result in compilation failures but fixes
  compatibility issues with C.

  The `libc` crate matches this change as of its 0.2.169 release.

- [When compiling a nested `macro_rules` macro from an external
  crate, the content of the inner `macro_rules` is now built with
  the edition of the external crate, not the local crate.]
  (rust-lang/rust#133274)
- [Increase `sparcv9-sun-solaris` and `x86_64-pc-solaris` Solaris
  baseline to 11.4.]
  (rust-lang/rust#133293)
- [Show `abi_unsupported_vector_types` lint in future breakage reports]
  (rust-lang/rust#133374)
- [Error if multiple super-trait instantiations of `dyn Trait` need
  associated types to be specified but only one is provided]
  (rust-lang/rust#133392)
- [Change `powerpc64-ibm-aix` default `codemodel` to large]
  (rust-lang/rust#133811)

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.

- [Build `x86_64-unknown-linux-gnu` with LTO for C/C++ code (e.g., `jemalloc`)]
  (rust-lang/rust#134690)

This MR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [rust](https://github.com/rust-lang/rust) | minor | `1.84.1` -> `1.85.0` |

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>

### [`v1.85.0`](https://github.com/rust-lang/rust/blob/HEAD/RELEASES.md#Version-1850-2025-02-20)

[Compare Source](rust-lang/rust@1.84.1...1.85.0)

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

<a id="1.85.0-Language"></a>

## Language

-   [The 2024 Edition is now stable.](rust-lang/rust#133349)
    See [the edition guide](https://doc.rust-lang.org/nightly/edition-guide/rust-2024/index.html) for more details.
-   [Stabilize async closures](rust-lang/rust#132706)
    See [RFC 3668](https://rust-lang.github.io/rfcs/3668-async-closures.html) for more details.
-   [Stabilize `#[diagnostic::do_not_recommend]`](rust-lang/rust#132056)
-   [Add `unpredictable_function_pointer_comparisons` lint to warn against function pointer comparisons](rust-lang/rust#118833)
-   [Lint on combining `#[no_mangle]` and `#[export_name]` attributes.](rust-lang/rust#131558)

<a id="1.85.0-Compiler"></a>

## Compiler

-   [The unstable flag `-Zpolymorphize` has been removed](rust-lang/rust#133883), see rust-lang/compiler-team#810 for some background.

<a id="1.85.0-Platform-Support"></a>

## Platform Support

-   [Promote `powerpc64le-unknown-linux-musl` to tier 2 with host tools](rust-lang/rust#133801)

Refer to Rust's \[platform support page]\[platform-support-doc]
for more information on Rust's tiered platform support.

<a id="1.85.0-Libraries"></a>

## Libraries

-   [Panics in the standard library now have a leading `library/` in their path](rust-lang/rust#132390)
-   [`std::env::home_dir()` on Windows now ignores the non-standard `$HOME` environment variable](rust-lang/rust#132515)

    It will be un-deprecated in a subsequent release.
-   [Add `AsyncFn*` to the prelude in all editions.](rust-lang/rust#132611)

<a id="1.85.0-Stabilized-APIs"></a>

## Stabilized APIs

-   [`BuildHasherDefault::new`](https://doc.rust-lang.org/stable/std/hash/struct.BuildHasherDefault.html#method.new)
-   [`ptr::fn_addr_eq`](https://doc.rust-lang.org/std/ptr/fn.fn_addr_eq.html)
-   [`io::ErrorKind::QuotaExceeded`](https://doc.rust-lang.org/stable/std/io/enum.ErrorKind.html#variant.QuotaExceeded)
-   [`io::ErrorKind::CrossesDevices`](https://doc.rust-lang.org/stable/std/io/enum.ErrorKind.html#variant.CrossesDevices)
-   [`{float}::midpoint`](https://doc.rust-lang.org/core/primitive.f32.html#method.midpoint)
-   [Unsigned `{integer}::midpoint`](https://doc.rust-lang.org/std/primitive.u64.html#method.midpoint)
-   [`NonZeroU*::midpoint`](https://doc.rust-lang.org/std/num/type.NonZeroU32.html#method.midpoint)
-   [impl `std::iter::Extend` for tuples with arity 1 through 12](https://doc.rust-lang.org/stable/std/iter/trait.Extend.html#impl-Extend%3C\(A,\)%3E-for-\(EA,\))
-   [`FromIterator<(A, ...)>` for tuples with arity 1 through 12](https://doc.rust-lang.org/stable/std/iter/trait.FromIterator.html#impl-FromIterator%3C\(EA,\)%3E-for-\(A,\))
-   [`std::task::Waker::noop`](https://doc.rust-lang.org/stable/std/task/struct.Waker.html#method.noop)

These APIs are now stable in const contexts:

-   [`mem::size_of_val`](https://doc.rust-lang.org/stable/std/mem/fn.size_of_val.html)
-   [`mem::align_of_val`](https://doc.rust-lang.org/stable/std/mem/fn.align_of_val.html)
-   [`Layout::for_value`](https://doc.rust-lang.org/stable/std/alloc/struct.Layout.html#method.for_value)
-   [`Layout::align_to`](https://doc.rust-lang.org/stable/std/alloc/struct.Layout.html#method.align_to)
-   [`Layout::pad_to_align`](https://doc.rust-lang.org/stable/std/alloc/struct.Layout.html#method.pad_to_align)
-   [`Layout::extend`](https://doc.rust-lang.org/stable/std/alloc/struct.Layout.html#method.extend)
-   [`Layout::array`](https://doc.rust-lang.org/stable/std/alloc/struct.Layout.html#method.array)
-   [`std::mem::swap`](https://doc.rust-lang.org/stable/std/mem/fn.swap.html)
-   [`std::ptr::swap`](https://doc.rust-lang.org/stable/std/ptr/fn.swap.html)
-   [`NonNull::new`](https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.new)
-   [`HashMap::with_hasher`](https://doc.rust-lang.org/stable/std/collections/struct.HashMap.html#method.with_hasher)
-   [`HashSet::with_hasher`](https://doc.rust-lang.org/stable/std/collections/struct.HashSet.html#method.with_hasher)
-   [`BuildHasherDefault::new`](https://doc.rust-lang.org/stable/std/hash/struct.BuildHasherDefault.html#method.new)
-   [`<float>::recip`](https://doc.rust-lang.org/stable/std/primitive.f32.html#method.recip)
-   [`<float>::to_degrees`](https://doc.rust-lang.org/stable/std/primitive.f32.html#method.to_degrees)
-   [`<float>::to_radians`](https://doc.rust-lang.org/stable/std/primitive.f32.html#method.to_radians)
-   [`<float>::max`](https://doc.rust-lang.org/stable/std/primitive.f32.html#method.max)
-   [`<float>::min`](https://doc.rust-lang.org/stable/std/primitive.f32.html#method.min)
-   [`<float>::clamp`](https://doc.rust-lang.org/stable/std/primitive.f32.html#method.clamp)
-   [`<float>::abs`](https://doc.rust-lang.org/stable/std/primitive.f32.html#method.abs)
-   [`<float>::signum`](https://doc.rust-lang.org/stable/std/primitive.f32.html#method.signum)
-   [`<float>::copysign`](https://doc.rust-lang.org/stable/std/primitive.f32.html#method.copysign)
-   [`MaybeUninit::write`](https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.write)

<a id="1.85.0-Cargo"></a>

## Cargo

-   [Add future-incompatibility warning against keywords in cfgs and add raw-idents](rust-lang/cargo#14671)
-   [Stabilize higher precedence trailing flags](rust-lang/cargo#14900)
-   [Pass `CARGO_CFG_FEATURE` to build scripts](rust-lang/cargo#14902)

<a id="1.85.0-Rustdoc"></a>

## Rustdoc

-   [Doc comment on impl blocks shows the first line, even when the impl block is collapsed](rust-lang/rust#132155)

<a id="1.85.0-Compatibility-Notes"></a>

## Compatibility Notes

-   [`rustc` no longer treats the `test` cfg as a well known check-cfg](rust-lang/rust#131729), instead it is up to the build systems and users of `--check-cfg`\[^check-cfg] to set it as a well known cfg using `--check-cfg=cfg(test)`.

    This is done to enable build systems like Cargo to set it conditionally, as not all source files are suitable for unit tests.
    [Cargo (for now) unconditionally sets the `test` cfg as a well known cfg](rust-lang/cargo#14963).
    \[^check-cfg]: https://doc.rust-lang.org/nightly/rustc/check-cfg.html
-   [Disable potentially incorrect type inference if there are trivial and non-trivial where-clauses](rust-lang/rust#132325)
-   `std::env::home_dir()` has been deprecated for years, because it can give surprising results in some Windows configurations if the `HOME` environment variable is set (which is not the normal configuration on Windows). We had previously avoided changing its behavior, out of concern for compatibility with code depending on this non-standard configuration. Given how long this function has been deprecated, we're now fixing its behavior as a bugfix. A subsequent release will remove the deprecation for this function.
-   [Make `core::ffi::c_char` signedness more closely match that of the platform-default `char`](rust-lang/rust#132975)

    This changed `c_char` from an `i8` to `u8` or vice versa on many Tier 2 and 3
    targets (mostly Arm and RISC-V embedded targets). The new definition may
    result in compilation failures but fixes compatibility issues with C.

    The `libc` crate matches this change as of its 0.2.169 release.
-   [When compiling a nested `macro_rules` macro from an external crate, the content of the inner `macro_rules` is now built with the edition of the external crate, not the local crate.](rust-lang/rust#133274)
-   [Increase `sparcv9-sun-solaris` and `x86_64-pc-solaris` Solaris baseline to 11.4.](rust-lang/rust#133293)
-   [Show `abi_unsupported_vector_types` lint in future breakage reports](rust-lang/rust#133374)
-   [Error if multiple super-trait instantiations of `dyn Trait` need associated types to be specified but only one is provided](rust-lang/rust#133392)
-   [Change `powerpc64-ibm-aix` default `codemodel` to large](rust-lang/rust#133811)

<a id="1.85.0-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.

-   [Build `x86_64-unknown-linux-gnu` with LTO for C/C++ code (e.g., `jemalloc`)](rust-lang/rust#134690)

</details>

---

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

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

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

---

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---

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