Improve type stability of src/range.jl

[odow]

x-ref #24

[codecov]

Codecov Report

❌ Patch coverage is 97.14286% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 95.36%. Comparing base (6c2ca24) to head (f7e7932).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
src/range.jl	97.14%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #28      +/-   ##
==========================================
- Coverage   96.00%   95.36%   -0.64%     
==========================================
  Files           4        4              
  Lines         400      388      -12     
==========================================
- Hits          384      370      -14     
- Misses         16       18       +2     

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