rustdoc: error out on --test with --emit

[notriddle]

These options don't behave reasonably when combined right now, and there are no tests and no docs for how they should.

For the short term, make this a fatal error. If we decide to assign this some semantics, then we can do that at any time.

[rustbot]

r? @fmease

rustbot has assigned @fmease.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

Why was this reviewer chosen?

The reviewer was selected based on:

• Owners of files modified in this PR: rustdoc
• rustdoc expanded to 9 candidates
• Random selection from GuillaumeGomez, camelid, fmease, lolbinarycat

[fmease]

Thanks! @bors r+ rollup

View changes since this review

[rust-bors]

📌 Commit 77eea39 has been approved by fmease

It is now in the queue for this repository.

[rust-bors]

☀️ Test successful - CI
Approved by: fmease
Duration: 3h 8m 12s
Pushing e0a8361 to main...

[github-actions]

What is this?

This is an experimental post-merge analysis report that shows differences in test outcomes between the merged PR and its parent PR.

Comparing 9f0615c (parent) -> e0a8361 (this PR)

Test differences

Show 2 test diffs

Stage 1

• [ui] tests/rustdoc-ui/doctest/emit-test.rs: [missing] -> pass (J0)

Stage 2

• [ui] tests/rustdoc-ui/doctest/emit-test.rs: [missing] -> pass (J1)

Job group index

• J0: x86_64-gnu-llvm-21-3
• J1: aarch64-apple, aarch64-gnu, aarch64-gnu-llvm-21-1, aarch64-msvc-1, i686-gnu-1, i686-gnu-nopt-1, i686-msvc-1, optional-x86_64-gnu-parallel-frontend, x86_64-gnu, x86_64-gnu-llvm-21-2, x86_64-gnu-nopt, x86_64-gnu-stable, x86_64-mingw-1, x86_64-msvc-1

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard e0a8361373c88bd791b5b1335c6cbf83cd68e4d5 --output-dir test-dashboard

And then open test-dashboard/index.html in your browser to see an overview of all executed tests.

Job duration changes

1. dist-aarch64-apple: 2h -> 1h 35m (-20.7%)
2. aarch64-apple: 3h 18m -> 2h 38m (-20.4%)
3. dist-aarch64-llvm-mingw: 1h 25m -> 1h 42m (+19.9%)
4. test-various: 1h 52m -> 2h 14m (+19.6%)
5. dist-apple-various: 1h 48m -> 1h 30m (-16.6%)
6. x86_64-mingw-1: 3h 6m -> 2h 41m (-13.0%)
7. x86_64-msvc-ext3: 1h 40m -> 1h 50m (+10.4%)
8. x86_64-gnu-distcheck: 2h 24m -> 2h 10m (-10.1%)
9. dist-x86_64-mingw: 2h 29m -> 2h 43m (+9.2%)
10. dist-x86_64-apple: 1h 49m -> 1h 59m (+9.0%)

How to interpret the job duration changes?

Job durations can vary a lot, based on the actual runner instance
that executed the job, system noise, invalidated caches, etc. The table above is provided
mostly for t-infra members, for simpler debugging of potential CI slow-downs.

[rust-timer]

Finished benchmarking commit (e0a8361): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results (secondary -2.2%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.2%	[-2.2%, -2.2%]	1
All ❌✅ (primary)	-	-	0

Cycles

Results (secondary 0.1%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	3.2%	[3.2%, 3.2%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.1%	[-3.1%, -3.1%]	1
All ❌✅ (primary)	-	-	0

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 484.991s -> 480.839s (-0.86%)
Artifact size: 396.79 MiB -> 396.90 MiB (0.03%)