codegen Propagate reported errors from ABI checks

[Dnreikronos]

Fixes #162814

The oversized array already gets an E0080 error. Normalization keeps the failed constant as an error marker in the buffer's type, though, and computing the constructor's return layout gives ReferencesError. The shared ABI handler then hits span_bug!, so we get an ICE on top of the useful error.

Handle ReferencesError by returning its existing ErrorGuaranteed. The ABI checks can then return through their usual error path, and mono collection stops before codegen. I think the shared handler is the right place for this because it already decides how to report ABI failures. Const-eval handles this variant by keeping the reported error too.

I reduced the async example to a small buffer constructor with no external crates. The test uses build-fail so it reaches the ABI checks, with default and optimized revisions to cover both paths.

Rebuilt the compiler and ran both new revisions plus the existing oversized-layout test. All three passed. Compiler checks and formatting passed too. Clippy completed with existing warnings allowed.

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[rust-log-analyzer]

The job test-tidy failed! Check out the build log: (web) (plain enhanced) (plain)

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extracting /checkout/obj/build/cache/2026-09-29/rustc-nightly-x86_64-unknown-linux-gnu.tar.xz to /checkout/obj/build/x86_64-unknown-linux-gnu/rustfmt
[TIMING:end] format::InternalRustfmt {  } -- 12.755
fmt: checked 7338 files
tidy check
tidy [ui_tests (tests)]: issue-number-only test names are not descriptive, consider renaming file `tests/ui/const-generics/gca/issue-162814.rs` to `{reason}-issue-162814.rs`
tidy [ui_tests (tests)]: FAIL
tidy [rustdoc_json (src)]: `rustdoc-json-types` modified, checking format version
tidy: Skipping binary file check, read-only filesystem
removing old virtual environment
creating virtual environment at '/checkout/obj/build/venv' using 'python3.12' and 'venv'
Requirement already satisfied: pip in ./build/venv/lib/python3.12/site-packages (24.0)
---
Running eslint on rustdoc JS files
info: ES-Check: checking 7 files...
info: ✓ ES-Check passed! All files are ES10 compatible.
typechecking javascript files
tidy: The following check failed: ui_tests (tests)
Command `/checkout/obj/build/x86_64-unknown-linux-gnu/stage1-tools-bin/rust-tidy --root-path=/checkout --cargo-path=/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo --output-dir=/checkout/obj/build --concurrency=4 --npm-path=/node/bin/yarn --ci=true --extra-checks=py,cpp,js,spellcheck` failed with exit code 1
Created at: src/bootstrap/src/core/build_steps/tool.rs:1627:23
Executed at: src/bootstrap/src/core/build_steps/test.rs:1747:29

Command has failed. Rerun with -v to see more details.
Bootstrap failed while executing `test src/tools/tidy tidyselftest --extra-checks=py,cpp,js,spellcheck`
Currently active steps:
test::Tidy {  } at src/bootstrap/src/core/build_steps/test.rs:1665
Build completed unsuccessfully in 0:02:37
  local time: Sat Oct  3 18:07:17 UTC 2026