Remove redundant casts

[FranciscoTGouveia]

If I am not overlooking anything, I believe these casts are redundant and can thus be safely removed.

For reference, this change was found by an optimizer developed as a research project.

CC @nunoplopes

Summary by CodeRabbit

• Refactor
  • Simplified internal metric vector construction for counters, gauges, and histograms.
  • Preserved existing behavior and error handling.

[ti-chi-bot]

Welcome @FranciscoTGouveia! It looks like this is your first PR to tikv/rust-prometheus 🎉

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• 27b281a chore: remove redundant casts

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 0e40646b-c723-4201-b03c-2dc6d11d3943

📥 Commits

Reviewing files that changed from the base of the PR and between 8151418 and 27b281a.

📒 Files selected for processing (3)

• src/counter.rs
• src/gauge.rs
• src/histogram.rs

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📝 Walkthrough

Walkthrough

The constructors for counter, gauge, and histogram vectors now return metric_vec directly. The redundant explicit casts were removed. Behavior and error handling remain unchanged.

Changes

Metric vector constructor returns

Layer / File(s)	Summary
Direct constructor returns src/counter.rs, src/gauge.rs, src/histogram.rs	GenericCounterVec::new, GenericGaugeVec::new, and HistogramVec::new return the created metric vector without an explicit cast.

Estimated code review effort: 1 (Trivial) | ~2 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the removal of redundant casts in the changed constructors.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[FranciscoTGouveia]

I have tried to find the CONTRIBUTING.md file (both before sending the patch and after the bot's suggestion), but to no avail.
Am I missing something?