Replace O(n) List.length comparisons with O(1) List.is_empty

[ishaan-arora-1]

Submission Checklist

• Run unit tests
• Documentation
  • If a user-facing facing change was made, the documentation PR is here: N/A
  • OR, no user-facing changes were made

Summary

Fixes #1591

Replace List.length l = 0 and List.length l > 0 with the idiomatic List.is_empty / not (List.is_empty ...) in two files:

• src/frontend/Warnings.ml: List.length warnings > 0 → not (List.is_empty warnings)
• src/analysis_and_optimization/Optimize.ml: 3 occurrences of List.length ... = 0 → List.is_empty ...

List.is_empty is O(1) while List.length traverses the entire list. The codebase already uses List.is_empty in 26+ other locations, making these remaining usages inconsistent with the established convention.

Release notes

Internal code quality improvement: replace O(n) List.length empty-checks with O(1) List.is_empty for consistency and minor performance improvement.

Copyright and Licensing

By submitting this pull request, the copyright holder is agreeing to
license the submitted work under the BSD 3-clause license (https://opensource.org/licenses/BSD-3-Clause)

AI Policy

This fix was very straightforwad, hence no AI involvement

[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 90.34%. Comparing base (0121e19) to head (cdab8c1).

Files with missing lines	Patch %	Lines
src/analysis_and_optimization/Optimize.ml	66.66%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1594   +/-   ##
=======================================
  Coverage   90.34%   90.34%           
=======================================
  Files          65       65           
  Lines       10027    10027           
=======================================
  Hits         9059     9059           
  Misses        968      968           

Files with missing lines	Coverage Δ
src/frontend/Warnings.ml	83.33% <100.00%> (ø)
src/analysis_and_optimization/Optimize.ml	92.44% <66.66%> (ø)

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[WardBrian]

Ah, I see the issue in Warning.ml. We probably don't want to open Core, since this brings in a lot of other stuff into scope. The smallest change is probably just using not (Core.List.is_empty ...

[ishaan-arora-1]

Ah, I see the issue in Warning.ml. We probably don't want to open Core, since this brings in a lot of other stuff into scope. The smallest change is probably just using not (Core.List.is_empty ...

oh alright, understood, ill try that

[WardBrian]

Thanks