C#: Don't suggest LINQ re-writes that would capture in, out, or ref parameters in a lambda. - #22541
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C#: Don't suggest LINQ re-writes that would capture in, out, or ref parameters in a lambda.#22541michaelnebel wants to merge 6 commits into
in, out, or ref parameters in a lambda.#22541michaelnebel wants to merge 6 commits into
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Copilot review overview
🟡 Changes recommended
The shared check omits separately modeled ref readonly parameters, allowing another uncompilable lambda rewrite.
Once you've addressed the issues Copilot identified, you can request another Copilot review.
Review tier: Balanced
Findings: 1
New issues introduced by this change (2)
| Severity | Finding |
|---|---|
 |
csharp/ql/lib/Linq/Helpers.qll — ref readonly parameters are modeled separately by Parameter.isReadonlyRef()… |
 |
csharp/ql/lib/Linq/Helpers.qll — Correct the typo and subject-verb agreement in this comment. |
What changed in this PR
Refactors shared LINQ opportunity detection and suppresses invalid lambda rewrites involving by-reference parameters.
Changes:
- Centralizes candidate-expression validation in reusable QL modules.
- Adds regression coverage and a change note.
| File | Description |
|---|---|
csharp/ql/lib/Linq/Helpers.qll |
Refactors detection and excludes by-reference captures. |
csharp/ql/src/change-notes/2026-09-10-missed-linq-inoutref.md |
Documents the analysis improvement. |
csharp/ql/test/query-tests/Linq/MissedAllOpportunity/MissedAllOpportunity.cs |
Adds All regression cases. |
csharp/ql/test/query-tests/Linq/MissedAllOpportunity/MissedAllOpportunity.expected |
Records expected All result. |
csharp/ql/test/query-tests/Linq/MissedAllOpportunity/MissedAllOpportunity.qlref |
Configures the All query test. |
csharp/ql/test/query-tests/Linq/MissedAllOpportunity/options |
Configures All test extraction. |
csharp/ql/test/query-tests/Linq/MissedFirstOrDefaultOpportunity/MissedFirstOrDefaultOpportunity.cs |
Tests ref-parameter suppression. |
csharp/ql/test/query-tests/Linq/MissedSelectOpportunity/MissedSelectOpportunity.cs |
Tests out-parameter suppression. |
csharp/ql/test/query-tests/Linq/MissedWhereOpportunity/MissedWhereOpportunity.cs |
Tests in-parameter suppression. |
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In this PR we
Helpers.qllfor thecs/linq/missed-*queries to enable sharing of logic.in,outorrefparameter is suggested.