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Fix RCS1118 to not report local variable passed as 'in' argument #1782

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josefpihrt merged 3 commits into from
Aug 1, 2026
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Fix RCS1118 to not report local variable passed as 'in' argument #1782

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d985a2a
Fix RCS1118 to not report local variable passed as 'in' argument
NoahStolk Aug 1, 2026
a89f88b
Add test for local variable passed to 'in' parameter without keyword
NoahStolk Aug 1, 2026
b482669
Update ChangeLog.md
NoahStolk Aug 1, 2026
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11 changes: 11 additions & 0 deletions src/Analyzers/CSharp/Analysis/MarkLocalVariableAsConst/MarkLocalVariableAsConstWalker.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,17 @@ public override void VisitAssignedExpression(ExpressionSyntax expression)
Result = true;
}

public override void VisitArgument(ArgumentSyntax node)
{
if (node.RefKindKeyword.IsKind(SyntaxKind.InKeyword)
&& IsLocalReference(node.Expression))
{
Result = true;
}

base.VisitArgument(node);
}

public override void VisitIdentifierName(IdentifierNameSyntax node)
{
if (node.IsParentKind(SyntaxKind.SimpleMemberAccessExpression, SyntaxKind.AddressOfExpression)
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36 changes: 36 additions & 0 deletions src/Tests/Analyzers.Tests/RCS1118MarkLocalVariableAsConstTests.cs
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Expand Up @@ -120,6 +120,42 @@ public static int Bar(this ref int p1, int p2)
{
return p1 + p2;
}
}");
}

[Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.MarkLocalVariableAsConst)]
public async Task TestNoDiagnostic_InArgument()
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{
await VerifyNoDiagnosticAsync(@"
public static class C
{
static void Foo()
{
int x = 0;
Bar(in x);
}

public static void Bar(in int p)
{
}
}");
}

[Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.MarkLocalVariableAsConst)]
public async Task TestNoDiagnostic_InArgument_RefReadOnlyParameter()
{
await VerifyNoDiagnosticAsync(@"
public static class C
{
static void Foo()
{
int x = 0;
Bar(in x);
}

public static void Bar(ref readonly int p)
{
}
}");
}
}