Fix MA0002 false positive on [with(StringComparer.Ordinal)] collection expression - #1237
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…ring comparer When using C# 15's `with(...)` syntax in a collection expression, e.g. `Dictionary<string, int> d = [with(StringComparer.Ordinal)]`, MA0002 was incorrectly reported because AnalyzeCollectionExpression only checked `Elements.Length == 0` and not `ConstructArguments`. Fix: Under ROSLYN_5_6_OR_GREATER, check whether ConstructArguments already contains a string comparer (IEqualityComparer<string> or IComparer<string>) and skip reporting in that case. Closes #1235 Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
This was referenced Jul 27, 2026
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Fixes #1235
Problem
Dictionary<string, List<string>> duplicates = [with(StringComparer.Ordinal)];was incorrectly flagged by MA0002 ("IEqualityComparer or IComparer is missing").Root Cause
AnalyzeCollectionExpressioncheckedElements.Length == 0but did not checkConstructArguments(C# 15'swith(...)arguments).In Roslyn's IOperation model for
[with(StringComparer.Ordinal)]:Elements.Length == 0(no key-value entries) → check passesConstructArguments.Length == 1(theStringComparer.Ordinal) → was not checkedSo the analyzer continued and incorrectly reported MA0002.
Fix
Under
#if ROSLYN_5_6_OR_GREATER(when C# 15'swith(...)syntax is available), checkConstructArgumentsfor an existingIEqualityComparer<string>orIComparer<string>. If already present, skip reporting.Tests added
[with(StringComparer.Ordinal)]→ no diagnostic ✓[with(10)](capacity only, no comparer) → still reports MA0002 ✓