Introduces the `arm64ec-pc-windows-msvc` target for building Arm64EC ("Emulation Compatible") binaries for Windows.

For more information about Arm64EC see <https://learn.microsoft.com/en-us/windows/arm/arm64ec>.

Tier 3 policy:

> A tier 3 target must have a designated developer or developers (the "target maintainers") on record to be CCed when issues arise regarding the target. (The mechanism to track and CC such developers may evolve over time.)

I will be the maintainer for this target.

> Targets must use naming consistent with any existing targets; for instance, a target for the same CPU or OS as an existing Rust target should use the same name for that CPU or OS. Targets should normally use the same names and naming conventions as used elsewhere in the broader ecosystem beyond Rust (such as in other toolchains), unless they have a very good reason to diverge. Changing the name of a target can be highly disruptive, especially once the target reaches a higher tier, so getting the name right is important even for a tier 3 target.

Target uses the `arm64ec` architecture to match LLVM and MSVC, and the `-pc-windows-msvc` suffix to indicate that it targets Windows via the MSVC environment.

> Target names should not introduce undue confusion or ambiguity unless absolutely necessary to maintain ecosystem compatibility. For example, if the name of the target makes people extremely likely to form incorrect beliefs about what it targets, the name should be changed or augmented to disambiguate it.

Target name exactly specifies the type of code that will be produced.

> If possible, use only letters, numbers, dashes and underscores for the name. Periods (.) are known to cause issues in Cargo.

Done.

> Tier 3 targets may have unusual requirements to build or use, but must not create legal issues or impose onerous legal terms for the Rust project or for Rust developers or users.

> The target must not introduce license incompatibilities.

Uses the same dependencies, requirements and licensing as the other `*-pc-windows-msvc` targets.

> Anything added to the Rust repository must be under the standard Rust license (MIT OR Apache-2.0).

Understood.

> The target must not cause the Rust tools or libraries built for any other host (even when supporting cross-compilation to the target) to depend on any new dependency less permissive than the Rust licensing policy. This applies whether the dependency is a Rust crate that would require adding new license exceptions (as specified by the tidy tool in the rust-lang/rust repository), or whether the dependency is a native library or binary. In other words, the introduction of the target must not cause a user installing or running a version of Rust or the Rust tools to be subject to any new license requirements.

> Compiling, linking, and emitting functional binaries, libraries, or other code for the target (whether hosted on the target itself or cross-compiling from another target) must not depend on proprietary (non-FOSS) libraries. Host tools built for the target itself may depend on the ordinary runtime libraries supplied by the platform and commonly used by other applications built for the target, but those libraries must not be required for code generation for the target; cross-compilation to the target must not require such libraries at all. For instance, rustc built for the target may depend on a common proprietary C runtime library or console output library, but must not depend on a proprietary code generation library or code optimization library. Rust's license permits such combinations, but the Rust project has no interest in maintaining such combinations within the scope of Rust itself, even at tier 3.

> "onerous" here is an intentionally subjective term. At a minimum, "onerous" legal/licensing terms include but are not limited to: non-disclosure requirements, non-compete requirements, contributor license agreements (CLAs) or equivalent, "non-commercial"/"research-only"/etc terms, requirements conditional on the employer or employment of any particular Rust developers, revocable terms, any requirements that create liability for the Rust project or its developers or users, or any requirements that adversely affect the livelihood or prospects of the Rust project or its developers or users.

Uses the same dependencies, requirements and licensing as the other `*-pc-windows-msvc` targets.

> Neither this policy nor any decisions made regarding targets shall create any binding agreement or estoppel by any party. If any member of an approving Rust team serves as one of the maintainers of a target, or has any legal or employment requirement (explicit or implicit) that might affect their decisions regarding a target, they must recuse themselves from any approval decisions regarding the target's tier status, though they may otherwise participate in discussions.

> This requirement does not prevent part or all of this policy from being cited in an explicit contract or work agreement (e.g. to implement or maintain support for a target). This requirement exists to ensure that a developer or team responsible for reviewing and approving a target does not face any legal threats or obligations that would prevent them from freely exercising their judgment in such approval, even if such judgment involves subjective matters or goes beyond the letter of these requirements.

Understood, I am not a member of the Rust team.

> Tier 3 targets should attempt to implement as much of the standard libraries as possible and appropriate (core for most targets, alloc for targets that can support dynamic memory allocation, std for targets with an operating system or equivalent layer of system-provided functionality), but may leave some code unimplemented (either unavailable or stubbed out as appropriate), whether because the target makes it impossible to implement or challenging to implement. The authors of pull requests are not obligated to avoid calling any portions of the standard library on the basis of a tier 3 target not implementing those portions.

Both `core` and `alloc` are supported.

Support for `std` dependends on making changes to the standard library, `stdarch` and `backtrace` which cannot be done yet as the bootstrapping compiler raises a warning ("unexpected `cfg` condition value") for `target_arch = "arm64ec"`.

> The target must provide documentation for the Rust community explaining how to build for the target, using cross-compilation if possible. If the target supports running binaries, or running tests (even if they do not pass), the documentation must explain how to run such binaries or tests for the target, using emulation if possible or dedicated hardware if necessary.

Documentation is provided in src/doc/rustc/src/platform-support/arm64ec-pc-windows-msvc.md

> Tier 3 targets must not impose burden on the authors of pull requests, or other developers in the community, to maintain the target. In particular, do not post comments (automated or manual) on a PR that derail or suggest a block on the PR based on a tier 3 target. Do not send automated messages or notifications (via any medium, including via @) to a PR author or others involved with a PR regarding a tier 3 target, unless they have opted into such messages.

> Backlinks such as those generated by the issue/PR tracker when linking to an issue or PR are not considered a violation of this policy, within reason. However, such messages (even on a separate repository) must not generate notifications to anyone involved with a PR who has not requested such notifications.

> Patches adding or updating tier 3 targets must not break any existing tier 2 or tier 1 target, and must not knowingly break another tier 3 target without approval of either the compiler team or the maintainers of the other tier 3 target.

> In particular, this may come up when working on closely related targets, such as variations of the same architecture with different features. Avoid introducing unconditional uses of features that another variation of the target may not have; use conditional compilation or runtime detection, as appropriate, to let each target run code supported by that target.

Understood.

Fixes rust-lang#120785

In the previous code, the success block of `lhs` would jump directly to the
success block of `rhs`. However, `rhs_success_block` could already contain
statements that are specific to the RHS, and the direct goto causes them to be
executed in the LHS success path as well.

This patch therefore creates a fresh block that the LHS and RHS success blocks
can both jump to.

We have `use Level::*;` in this file.

Removes unused `typeid_for_fnsig` for simplifying the compiler CFI API.

By just emitting them immediately, because it does happen in practice,
when errors are downgraded to delayed bugs.

We already had one case in `lint.rs` where we handled this at the
callsite. This commit changes things so it's handled within
`stash_diagnostic` instead, because rust-lang#121812 identified a second case,
and it's possible there are more.

Fixes rust-lang#121812.

…ate check

Add arm64ec-pc-windows-msvc target

Introduces the `arm64ec-pc-windows-msvc` target for building Arm64EC ("Emulation Compatible") binaries for Windows.

For more information about Arm64EC see <https://learn.microsoft.com/en-us/windows/arm/arm64ec>.

## Tier 3 policy:

> A tier 3 target must have a designated developer or developers (the "target maintainers") on record to be CCed when issues arise regarding the target. (The mechanism to track and CC such developers may evolve over time.)

I will be the maintainer for this target.

> Targets must use naming consistent with any existing targets; for instance, a target for the same CPU or OS as an existing Rust target should use the same name for that CPU or OS. Targets should normally use the same names and naming conventions as used elsewhere in the broader ecosystem beyond Rust (such as in other toolchains), unless they have a very good reason to diverge. Changing the name of a target can be highly disruptive, especially once the target reaches a higher tier, so getting the name right is important even for a tier 3 target.

Target uses the `arm64ec` architecture to match LLVM and MSVC, and the `-pc-windows-msvc` suffix to indicate that it targets Windows via the MSVC environment.

> Target names should not introduce undue confusion or ambiguity unless absolutely necessary to maintain ecosystem compatibility. For example, if the name of the target makes people extremely likely to form incorrect beliefs about what it targets, the name should be changed or augmented to disambiguate it.

Target name exactly specifies the type of code that will be produced.

> If possible, use only letters, numbers, dashes and underscores for the name. Periods (.) are known to cause issues in Cargo.

Done.

> Tier 3 targets may have unusual requirements to build or use, but must not create legal issues or impose onerous legal terms for the Rust project or for Rust developers or users.

> The target must not introduce license incompatibilities.

Uses the same dependencies, requirements and licensing as the other `*-pc-windows-msvc` targets.

> Anything added to the Rust repository must be under the standard Rust license (MIT OR Apache-2.0).

Understood.

> The target must not cause the Rust tools or libraries built for any other host (even when supporting cross-compilation to the target) to depend on any new dependency less permissive than the Rust licensing policy. This applies whether the dependency is a Rust crate that would require adding new license exceptions (as specified by the tidy tool in the rust-lang/rust repository), or whether the dependency is a native library or binary. In other words, the introduction of the target must not cause a user installing or running a version of Rust or the Rust tools to be subject to any new license requirements.

> Compiling, linking, and emitting functional binaries, libraries, or other code for the target (whether hosted on the target itself or cross-compiling from another target) must not depend on proprietary (non-FOSS) libraries. Host tools built for the target itself may depend on the ordinary runtime libraries supplied by the platform and commonly used by other applications built for the target, but those libraries must not be required for code generation for the target; cross-compilation to the target must not require such libraries at all. For instance, rustc built for the target may depend on a common proprietary C runtime library or console output library, but must not depend on a proprietary code generation library or code optimization library. Rust's license permits such combinations, but the Rust project has no interest in maintaining such combinations within the scope of Rust itself, even at tier 3.

> "onerous" here is an intentionally subjective term. At a minimum, "onerous" legal/licensing terms include but are not limited to: non-disclosure requirements, non-compete requirements, contributor license agreements (CLAs) or equivalent, "non-commercial"/"research-only"/etc terms, requirements conditional on the employer or employment of any particular Rust developers, revocable terms, any requirements that create liability for the Rust project or its developers or users, or any requirements that adversely affect the livelihood or prospects of the Rust project or its developers or users.

Uses the same dependencies, requirements and licensing as the other `*-pc-windows-msvc` targets.

> Neither this policy nor any decisions made regarding targets shall create any binding agreement or estoppel by any party. If any member of an approving Rust team serves as one of the maintainers of a target, or has any legal or employment requirement (explicit or implicit) that might affect their decisions regarding a target, they must recuse themselves from any approval decisions regarding the target's tier status, though they may otherwise participate in discussions.

> This requirement does not prevent part or all of this policy from being cited in an explicit contract or work agreement (e.g. to implement or maintain support for a target). This requirement exists to ensure that a developer or team responsible for reviewing and approving a target does not face any legal threats or obligations that would prevent them from freely exercising their judgment in such approval, even if such judgment involves subjective matters or goes beyond the letter of these requirements.

Understood, I am not a member of the Rust team.

> Tier 3 targets should attempt to implement as much of the standard libraries as possible and appropriate (core for most targets, alloc for targets that can support dynamic memory allocation, std for targets with an operating system or equivalent layer of system-provided functionality), but may leave some code unimplemented (either unavailable or stubbed out as appropriate), whether because the target makes it impossible to implement or challenging to implement. The authors of pull requests are not obligated to avoid calling any portions of the standard library on the basis of a tier 3 target not implementing those portions.

Both `core` and `alloc` are supported.

Support for `std` depends on making changes to the standard library, `stdarch` and `backtrace` which cannot be done yet as they require fixes coming in LLVM 18.

> The target must provide documentation for the Rust community explaining how to build for the target, using cross-compilation if possible. If the target supports running binaries, or running tests (even if they do not pass), the documentation must explain how to run such binaries or tests for the target, using emulation if possible or dedicated hardware if necessary.

Documentation is provided in src/doc/rustc/src/platform-support/arm64ec-pc-windows-msvc.md

> Tier 3 targets must not impose burden on the authors of pull requests, or other developers in the community, to maintain the target. In particular, do not post comments (automated or manual) on a PR that derail or suggest a block on the PR based on a tier 3 target. Do not send automated messages or notifications (via any medium, including via ```@)``` to a PR author or others involved with a PR regarding a tier 3 target, unless they have opted into such messages.

> Backlinks such as those generated by the issue/PR tracker when linking to an issue or PR are not considered a violation of this policy, within reason. However, such messages (even on a separate repository) must not generate notifications to anyone involved with a PR who has not requested such notifications.

> Patches adding or updating tier 3 targets must not break any existing tier 2 or tier 1 target, and must not knowingly break another tier 3 target without approval of either the compiler team or the maintainers of the other tier 3 target.

> In particular, this may come up when working on closely related targets, such as variations of the same architecture with different features. Avoid introducing unconditional uses of features that another variation of the target may not have; use conditional compilation or runtime detection, as appropriate, to let each target run code supported by that target.

Understood.

…nethercote

Improve error messages for generics with default parameters

Fixes rust-lang#120785

Issue: Previously, all type parameters with default types were deliberately ignored to simplify error messages. For example, an error message for Box type would display `Box<T>` instead of `Box<T, _>`. But, this resulted in unclear error message when a concrete type was used instead of the default type.

Fix: This PR fixes it by checking if a concrete type is specified after a default type to display the entire type name or the simplified type name.

…472,compiler-errors

Add tidy check for .stderr/.stdout files for non-existent test revisions

Closes rust-lang#77498.

…-mutex-unlock, r=jhpratt

Remove `Mutex::unlock` Function

As of the completion of the FCP in rust-lang#81872 (comment), it has come to the conclusion to be closed.

This PR removes the function entirely in light of the above.

Closes rust-lang#81872.

Stop using Bubble in coherence and instead emulate it with an intercrte check

r? `@compiler-errors`

This change is kinda funny, because all I've done is reimplement `Bubble` behaviour for coherence without using `Bubble` explicitly.

Make the success arms of `if lhs || rhs` meet up in a separate block

Extracted from rust-lang#118305, where this is necessary to avoid introducing a bug when injecting marker statements into the then/else arms.

---

In the previous code (rust-lang#111752), the success block of `lhs` would jump directly to the success block of `rhs`. However, `rhs_success_block` could already contain statements that are specific to the RHS, and the direct goto causes them to be executed in the LHS success path as well.

This patch therefore creates a fresh block that the LHS and RHS success blocks can both jump to.

---

I think the reason we currently get away with this is that `rhs_success_block` usually doesn't contain anything other than StorageDead statements for locals used by the RHS, and those statements don't seem to cause problems in the LHS success path (which never makes those locals live).

But if we start adding meaningful statements for branch coverage (or MC/DC coverage), it's important to keep the LHS and RHS blocks separate.

…eid-for-fnsig, r=workingjubilee

CFI: Remove unused `typeid_for_fnsig`

Removes unused `typeid_for_fnsig` for simplifying the compiler CFI API.

Handle stashing of delayed bugs

By just emitting them immediately, because it does happen in practice, when errors are downgraded to delayed bugs.

We already had one case in `lint.rs` where we handled this at the callsite. This commit changes things so it's handled within `stash_diagnostic` instead, because rust-lang#121812 identified a second case, and it's possible there are more.

Fixes rust-lang#121812.

r? `@oli-obk`

Implement missing ABI structures in StableMIR

Add implementations for Scalar, Primitive and WrappingRange for StableMIR.

FYI, I thought about reusing the `rustc_abi` module, since it is designed to not necessarily depend on the `rustc` internals, but the maintenance burden to maintain this crate in crates.io doesn't seem worth it at this point.

Fixes rust-lang/project-stable-mir#58

Remove unused fluent messages

Unused fluent messages after rust-lang#121779

Fix typo in comment

"pop" should have been "prop"