Rollup of 3 pull requests

src/ci/docker/host-x86_64/optional-x86_64-gnu-autodiff/Dockerfile

@@ -0,0 +1,39 @@
+FROM ubuntu:24.04
+
+ARG DEBIAN_FRONTEND=noninteractive
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    g++ \
+    make \
+    ninja-build \
+    file \
+    curl \
+    ca-certificates \
+    python3 \
+    git \
+    cmake \
+    pkg-config \
+    xz-utils \
+    zlib1g-dev \
+    && rm -rf /var/lib/apt/lists/*
+
+COPY scripts/sccache.sh /scripts/
+RUN sh /scripts/sccache.sh
+
+ENV NO_DOWNLOAD_CI_LLVM 1
+ENV CODEGEN_BACKENDS llvm
+
+ENV RUST_CONFIGURE_ARGS \
+    --build=x86_64-unknown-linux-gnu \
+    --enable-llvm-enzyme \
+    --enable-llvm-link-shared \
+    --enable-ninja \
+    --enable-option-checking \
+    --disable-docs \
+    --set llvm.download-ci-llvm=false
+
+ENV SCRIPT="../x.py test --stage 2 --no-fail-fast \
+    tests/codegen-llvm/autodiff \
+    tests/pretty/autodiff \
+    tests/ui/autodiff \
+    tests/ui/feature-gates/feature-gate-autodiff.rs"

src/ci/github-actions/jobs.yml

@@ -469,6 +469,11 @@ auto:
   - name: x86_64-gnu-miri
     <<: *job-linux-4c
 
+  - name: optional-x86_64-gnu-autodiff
+    continue_on_error: true
+    doc_url: https://rustc-dev-guide.rust-lang.org/tests/autodiff-ci-job.html
+    <<: *job-linux-4c
+
   ####################
   #  macOS Builders  #
   ####################

src/doc/rustc-dev-guide/src/SUMMARY.md

@@ -35,6 +35,7 @@
         - [Cranelift codegen backend](./tests/codegen-backend-tests/cg_clif.md)
         - [GCC codegen backend](./tests/codegen-backend-tests/cg_gcc.md)
     - [Performance testing](./tests/perf.md)
+    - [Autodiff CI job](./tests/autodiff-ci-job.md)
     - [Pre-stabilization CI job for the next solver and polonius alpha](./tests/x86_64-gnu-next-trait-solver-polonius-ci-job.md)
     - [Misc info](./tests/misc.md)
 - [Debugging the compiler](./compiler-debugging.md)

src/doc/rustc-dev-guide/src/tests/autodiff-ci-job.md

@@ -0,0 +1,45 @@
+# Autodiff CI job
+
+The [`optional-x86_64-gnu-autodiff`] job provides continuous test coverage for
+the experimental `autodiff` feature and its integration with LLVM Enzyme. It is
+an optional [auto job](./ci.md#auto-builds), so a failure does not prevent a
+pull request from being merged.
+
+For more context about the feature, see the [autodiff tracking issue] and the
+[autodiff internals](../autodiff/internals.md) chapter.
+
+## What is tested
+
+The job checks:
+
+- forward- and reverse-mode macro expansion and diagnostics;
+- LLVM IR generation for autodiff;
+- enforcement of the `autodiff` feature gate.
+
+## Running the job
+
+To run the job in a try build, comment on a pull request:
+
+```text
+@bors try jobs=optional-x86_64-gnu-autodiff
+```
+
+To run the job locally, run this command from a Rust checkout:
+
+```console
+$ cargo run --manifest-path src/ci/citool/Cargo.toml run-local optional-x86_64-gnu-autodiff
+```
+
+See [Testing with Docker](./docker.md) for more information about running CI
+jobs locally.
+
+## Point of contact
+
+If you have questions or need help with a failure in this job, open a new topic
+in the [autodiff Zulip channel]. For suspected Enzyme backend failures, see the
+[autodiff debugging guide].
+
+[autodiff Zulip channel]: https://rust-lang.zulipchat.com/#narrow/channel/390790-wg-autodiff
+[autodiff debugging guide]: ../autodiff/debugging.md
+[autodiff tracking issue]: https://github.com/rust-lang/rust/issues/124509
+[`optional-x86_64-gnu-autodiff`]: https://github.com/rust-lang/rust/blob/HEAD/src/ci/github-actions/jobs.yml

tests/ui/issues/issue-51655.rs → tests/ui/consts/const_in_pattern/const-bytes-slice-pattern.rs

@@ -1,4 +1,7 @@
+//! Regression test for <https://github.com/rust-lang/rust/issues/51655>.
+//! This used to ICE.
 //@ check-pass
+
 #![allow(dead_code)]
 
 const PATH_DOT: &[u8] = &[b'.'];

tests/ui/crate-loading/missing-target-error.rs

@@ -0,0 +1,13 @@
+//! Regression test for <https://github.com/rust-lang/rust/issues/37131>.
+//! Tests that compiling for a target which is not installed will result in a helpful
+//! error message.
+//~^^^ ERROR can't find crate for `std`
+//~| NOTE target may not be installed
+//~| NOTE can't find crate
+
+//@ compile-flags: --target=thumbv6m-none-eabi
+//@ ignore-arm
+//@ needs-llvm-components: arm
+//@ ignore-backends: gcc
+
+fn main() { }

tests/ui/issues/issue-24687-embed-debuginfo/auxiliary/issue-24687-mbcs-in-comments.rs → tests/ui/debuginfo/auxiliary/cross-crate-multibyte-debuginfo-comments.rs

@@ -1,9 +1,10 @@
-use std::fmt;
+//! Auxiliary file for <https://github.com/rust-lang/rust/issues/24687>.
+//! This is a file with many multi-byte characters, to try to encourage
+//! the compiler to trip on them. The Drop implementation below will
+//! need to have its source location embedded into the debug info for
+//! the output file.
 
-// This ia file with many multi-byte characters, to try to encourage
-// the compiler to trip on them.  The Drop implementation below will
-// need to have its source location embedded into the debug info for
-// the output file.
+use std::fmt;
 
 // αααααααααααααααααααααααααααααααααααααααααααααααααααααααααααααααααααααα
 // ββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββ

tests/ui/debuginfo/auxiliary/cross-crate-multibyte-debuginfo.rs

@@ -0,0 +1,10 @@
+//! Auxiliary file for <https://github.com/rust-lang/rust/issues/24687>.
+//! This is a file that pulls in a separate file as a submodule, where
+//! that separate file has many multi-byte characters, to try to
+//! encourage the compiler to trip on them.
+#![crate_type="lib"]
+
+#[path = "cross-crate-multibyte-debuginfo-comments.rs"]
+mod issue_24687_mbcs_in_comments;
+
+pub use issue_24687_mbcs_in_comments::D;

tests/ui/issues/issue-24687-embed-debuginfo/main.rs → tests/ui/debuginfo/cross-crate-multibyte-debuginfo.rs

@@ -1,8 +1,9 @@
+//! Regression test for <https://github.com/rust-lang/rust/issues/24687>.
 //@ run-pass
-//@ aux-build:issue-24687-lib.rs
+//@ aux-build:cross-crate-multibyte-debuginfo.rs
 //@ compile-flags:-g
 
-extern crate issue_24687_lib as d;
+extern crate cross_crate_multibyte_debuginfo as d;
 
 fn main() {
     // Create a `D`, which has a destructor whose body will be codegen'ed

tests/ui/issues/issue-37510.rs → tests/ui/expr/if/mut-borrow-in-else-if-after-if-let.rs

@@ -1,3 +1,5 @@
+//! Regression test for <https://github.com/rust-lang/rust/issues/37510>.
+//! Test that else-if after if-let is not considered a pattern guard.
 //@ check-pass
 
 fn foo(_: &mut i32) -> bool { true }

tests/ui/issues/issue-50618.rs → tests/ui/functional-struct-update/fru-unknown-field-in-closure.rs

@@ -1,3 +1,6 @@
+//! Regression test for <https://github.com/rust-lang/rust/issues/50618>.
+//! This used to ICE.
+
 struct Point {
     pub x: u64,
     pub y: u64,

tests/ui/issues/issue-50618.stderr → tests/ui/functional-struct-update/fru-unknown-field-in-closure.stderr

@@ -1,5 +1,5 @@
 error[E0560]: struct `Point` has no field named `nonexistent`
-  --> $DIR/issue-50618.rs:14:13
+  --> $DIR/fru-unknown-field-in-closure.rs:17:13
    |
 LL |             nonexistent: 0,
    |             ^^^^^^^^^^^ `Point` does not have this field

tests/ui/issues/issue-38556.rs → tests/ui/imports/macro-use-as.rs

@@ -1,4 +1,7 @@
+//! Regression test for <https://github.com/rust-lang/rust/issues/38556>.
+//! Reexport in macro caused ICE.
 //@ run-pass
+
 #![allow(dead_code)]
 pub struct Foo;
 

tests/ui/issues/issue-51116.rs → tests/ui/inference/need_type_info/for-loop-nested-array-inference.rs

@@ -1,3 +1,6 @@
+//! Regression test for <https://github.com/rust-lang/rust/issues/51116>.
+//! This used to leak internal `__next` ident into suggestion.
+
 fn main() {
     let tiles = Default::default();
     for row in &mut tiles {

tests/ui/issues/issue-51116.stderr → tests/ui/inference/need_type_info/for-loop-nested-array-inference.stderr

@@ -1,5 +1,5 @@
 error[E0282]: type annotations needed
-  --> $DIR/issue-51116.rs:5:13
+  --> $DIR/for-loop-nested-array-inference.rs:8:13
    |
 LL |             *tile = 0;
    |             ^^^^^ cannot infer type

tests/ui/issues/issue-37884.rs → tests/ui/lifetimes/lifetime-errors/iterator-next-extra-named-lifetime.rs

@@ -1,3 +1,5 @@
+//! Regression test for <https://github.com/rust-lang/rust/issues/37884>.
+//! This used to leak compiler data structures in error message.
 //@ dont-require-annotations: NOTE
 
 struct RepeatMut<'a, T>(T, &'a ());

tests/ui/issues/issue-37884.stderr → tests/ui/lifetimes/lifetime-errors/iterator-next-extra-named-lifetime.stderr

@@ -1,5 +1,5 @@
 error[E0308]: method not compatible with trait
-  --> $DIR/issue-37884.rs:8:5
+  --> $DIR/iterator-next-extra-named-lifetime.rs:10:5
    |
 LL |     fn next(&'a mut self) -> Option<Self::Item>
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ lifetime mismatch
@@ -9,7 +9,7 @@ LL |     fn next(&'a mut self) -> Option<Self::Item>
 note: the anonymous lifetime as defined here...
   --> $SRC_DIR/core/src/iter/traits/iterator.rs:LL:COL
 note: ...does not necessarily outlive the lifetime `'a` as defined here
-  --> $DIR/issue-37884.rs:5:6
+  --> $DIR/iterator-next-extra-named-lifetime.rs:7:6
    |
 LL | impl<'a, T: 'a> Iterator for RepeatMut<'a, T> {
    |      ^^

tests/ui/issues/issue-5067.rs → tests/ui/macros/repetition-matches-empty-token-tree.rs

@@ -1,10 +1,11 @@
-#![allow(unused_macros)]
-
-// Tests that repetition matchers cannot match the empty token tree (since that would be
-// ambiguous).
+//! Regression test for <https://github.com/rust-lang/rust/issues/5067>.
+//! Tests that repetition matchers cannot match the empty token tree (since that would be
+//! ambiguous).
 
 //@ edition:2018
 
+#![allow(unused_macros)]
+
 macro_rules! foo {
     ( $()* ) => {};
     //~^ ERROR repetition matches empty token tree