C#: Add change note.

aschackmull · aschackmull · commit 84a65bef4353 · 2025-10-03T16:29:56.000+02:00
diff --git a/csharp/ql/lib/change-notes/2025-10-03-nullness.md b/csharp/ql/lib/change-notes/2025-10-03-nullness.md
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+---
+category: majorAnalysis
+---
+* The representation of the C# control-flow graph has been significantly changed. This has minor effects on a wide range of queries including both minor improvements and minor regressions, for example, improved precision has been observed for `cs/inefficient-containskey` and `cs/stringbuilder-creation-in-loop`. Two queries stand out as being significantly affected with great improvements: `cs/dereferenced-value-may-be-null` has been completely rewritten which removes a very significant number of false positives. Furthermore, `cs/constant-condition` has been updated to report many new results - these new results are primarily expected to be true positives, but a few new false positives are expected as well. As part of these changes, `cs/dereferenced-value-may-be-null` has been changed from a `path-problem` query to a `problem` query, so paths are no longer reported for this query.

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 +---
 +category: majorAnalysis
 +---
 +* The representation of the C# control-flow graph has been significantly changed. This has minor effects on a wide range of queries including both minor improvements and minor regressions, for example, improved precision has been observed for `cs/inefficient-containskey` and `cs/stringbuilder-creation-in-loop`. Two queries stand out as being significantly affected with great improvements: `cs/dereferenced-value-may-be-null` has been completely rewritten which removes a very significant number of false positives. Furthermore, `cs/constant-condition` has been updated to report many new results - these new results are primarily expected to be true positives, but a few new false positives are expected as well. As part of these changes, `cs/dereferenced-value-may-be-null` has been changed from a `path-problem` query to a `problem` query, so paths are no longer reported for this query.