track_caller for slice length assertions

[kornelski]

clone_from_slice was missing #[track_caller], and its assert did not report a useful location.

These are small generic methods, so hopefully track_caller gets inlined into nothingness, but it may be worth running a benchmark on this.

[rust-highfive]

r? @dtolnay

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[the8472]

@bors try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

@rustbot label: +S-waiting-on-perf

[bors]

⌛ Trying commit 90ea93b with merge 8009f83223e622efca45794a43b6b2a3c67fc8f9...

[bors]

☀️ Try build successful - checks-actions
Build commit: 8009f83223e622efca45794a43b6b2a3c67fc8f9 (8009f83223e622efca45794a43b6b2a3c67fc8f9)

[rust-timer]

Queued 8009f83223e622efca45794a43b6b2a3c67fc8f9 with parent 3c8f001, future comparison URL.

[rust-timer]

Finished benchmarking commit (8009f83223e622efca45794a43b6b2a3c67fc8f9): comparison url.

Summary: This benchmark run did not return any relevant changes.

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR led to changes in compiler perf.

@bors rollup=never
@rustbot label: +S-waiting-on-review -S-waiting-on-perf -perf-regression

[joshtriplett]

@bors r+

[bors]

📌 Commit 90ea93b has been approved by joshtriplett

[bors]

⌛ Testing commit 90ea93b with merge 0a09858...

[bors]

☀️ Test successful - checks-actions
Approved by: joshtriplett
Pushing 0a09858 to master...

[rust-timer]

Finished benchmarking commit (0a09858): comparison url.

Summary: This benchmark run did not return any relevant changes.

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

@rustbot label: -perf-regression