[sylvestre]

An invalid back-reference such as s/\(a\)/\2/ is only detected after the flags are parsed, so the UUTILS_DIAG caret landed past the end of the command. It now points at the \2, including when the replacement spans several lines.

$ UUTILS_DIAG=always sed 's/\(a\)/\2/'
sed: <script argument 1>:1:9: error: invalid reference \2 on `s' command's RHS
   ╭─[ <script argument 1>:1:9 ]
   │
 1 │ s/\(a\)/\2/
   │         ─
───╯

[Copilot]

🟢 Approval recommended

The focused change preserves validation behavior and adds regression coverage, with no unresolved findings.

No open issues 🎉

What changed in this PR

Corrects sed’s invalid back-reference diagnostic so the caret points at the offending reference rather than past the command.

Changes:

• Records the first occurrence of the highest-numbered replacement reference.
• Uses that location for validation errors.
• Adds a regression test for caret placement.

File	Description
tests/​by-util/​test_sed.rs	Tests caret placement with repeated references.
src/​sed/​compiler.rs	Captures and uses the reference’s source location.
src/​sed/​command.rs	Stores an optional location in replacement templates.

_{Review effort: Balanced}

[codecov]

Codecov Report

❌ Patch coverage is 93.33333% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 94.84%. Comparing base (b1ea0dc) to head (6ac57c8).

Files with missing lines	Patch %	Lines
src/sed/compiler.rs	92.85%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #609      +/-   ##
==========================================
- Coverage   94.85%   94.84%   -0.01%     
==========================================
  Files          14       14              
  Lines        7230     7236       +6     
  Branches      432      432              
==========================================
+ Hits         6858     6863       +5     
- Misses        371      372       +1     
  Partials        1        1              

Flag	Coverage Δ
macos_latest	96.38% <93.33%> (-0.02%)	⬇️
ubuntu_latest	96.32% <93.33%> (-0.02%)	⬇️
windows_latest	0.00% <0.00%> (ø)

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[codspeed]

Merging this PR will improve performance by 7.69%

⚠️ 1 benchmark spent significant time in system calls

System calls cannot be consistently instrumented, so they are not included in the measure, which understates the real cost. Please switch to the Walltime instrument to accurately measure system calls.

Measurement and system calls

• access_log_append

⚡ 2 improved benchmarks
✅ 9 untouched benchmarks

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
⚡	number_fix	1.3 s	1.2 s	+12.01%
⚡	access_log_subst	2.2 s	2.1 s	+3.55%

Tip

Curious why performance improved? Comment @codspeedbot explain why performance improved on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing sylvestre:sed-backref-caret (6ac57c8) with main (b1ea0dc)}