Clarify UTF-16 decoding errors

[jnodorp]

Fix UTF-16 error messages as suggested in #116258.

[rustbot]

r? @joboet

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

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[bors]

☔ The latest upstream changes (presumably #149836) made this pull request unmergeable. Please resolve the merge conflicts.

[joboet]

Implementation-wise this looks fine (modulo the nit). I'll reassign this to libs-api though, in case they have comments...

r? libs-api

[rustbot]

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

[SimonSapin]

@bors r+

I’m not part of libs-api but they’ve had ample opportunity to comment. I’ll take it on myself to evaluate that this PR correctly addresses the one blocking FCP concern from #116258 (comment)

[rust-bors]

📌 Commit f7444d4 has been approved by SimonSapin

It is now in the queue for this repository.

[rust-bors]

☀️ Test successful - CI
Approved by: SimonSapin
Duration: 3h 22m 54s
Pushing 5ea817c 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 a31c27a (parent) -> 5ea817c (this PR)

Test differences

Show 307 test diffs

307 doctest diffs were found. These are ignored, as they are noisy.

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard 5ea817c65e4896167300b7d2550781b98da9901a --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. i686-msvc-2: 1h 41m -> 2h 17m (+35.2%)
2. aarch64-apple: 2h 38m -> 3h 15m (+23.3%)
3. dist-arm-linux-gnueabi: 1h 12m -> 1h 28m (+22.9%)
4. pr-check-1: 33m 45s -> 26m 54s (-20.3%)
5. optional-x86_64-gnu-parallel-frontend: 2h 48m -> 2h 21m (-16.3%)
6. i686-gnu-1: 2h 26m -> 2h 4m (-15.5%)
7. i686-gnu-2: 1h 46m -> 1h 30m (-15.3%)
8. x86_64-rust-for-linux: 55m 47s -> 47m 24s (-15.0%)
9. aarch64-msvc-2: 2h -> 1h 43m (-14.4%)
10. x86_64-gnu-llvm-21-1: 57m 33s -> 49m 25s (-14.1%)

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 (5ea817c): comparison URL.

Overall result: ✅ improvements - no action needed

@rustbot label: -perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.0%	[-0.0%, -0.0%]	1
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (secondary -1.5%)

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)	2.2%	[2.2%, 2.2%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.3%	[-5.7%, -0.9%]	2
All ❌✅ (primary)	-	-	0

Cycles

Results (primary -0.3%)

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

	mean	range	count
Regressions ❌ (primary)	2.0%	[2.0%, 2.0%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-2.6%	[-2.6%, -2.6%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.3%	[-2.6%, 2.0%]	2

Binary size

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)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.1%	[-0.1%, -0.1%]	1
All ❌✅ (primary)	-	-	0

Bootstrap: 510.693s -> 511.688s (0.19%)
Artifact size: 400.56 MiB -> 400.54 MiB (-0.01%)