Fix analyzer RCS1105 (#1669)

Author: josefpihrt

ChangeLog.md

@@ -17,6 +17,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fix analyzer [RCS1229](https://josefpihrt.github.io/docs/roslynator/analyzers/RCS1229) ([PR](https://github.com/dotnet/roslynator/pull/1667))
 - Fix analyzer [RCS1250](https://josefpihrt.github.io/docs/roslynator/analyzers/RCS1250) ([PR](https://github.com/dotnet/roslynator/pull/1652) by @aihnatiuk)
 - Fix analyzer [RCS1260](https://josefpihrt.github.io/docs/roslynator/analyzers/RCS1260) ([PR](https://github.com/dotnet/roslynator/pull/1668))
+- Fix analyzer [RCS1105](https://josefpihrt.github.io/docs/roslynator/analyzers/RCS1105) ([PR](https://github.com/dotnet/roslynator/pull/1669))
 
 ## [4.13.1] - 2025-02-23
 

src/Analyzers/CSharp/Analysis/UnnecessaryInterpolationAnalyzer.cs

@@ -53,6 +53,14 @@ private static void AnalyzeInterpolation(SyntaxNodeAnalysisContext context)
         if (interpolatedString.StringStartToken.ValueText.Contains("@") != stringLiteralInfo.IsVerbatim)
             return;
 
+#if ROSLYN_4_2
+        if (interpolatedString.StringStartToken.IsKind(SyntaxKind.InterpolatedSingleLineRawStringStartToken, SyntaxKind.InterpolatedMultiLineRawStringStartToken)
+            && stringLiteralInfo.ContainsEscapeSequence)
+        {
+            return;
+        }
+#endif
+
         DiagnosticHelpers.ReportDiagnostic(context, DiagnosticRules.UnnecessaryInterpolation, interpolation);
     }
 }

src/Tests/Analyzers.Tests/RCS1105UnnecessaryInterpolationTests.cs

@@ -0,0 +1,26 @@
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis;
+using Roslynator.CSharp.CodeFixes;
+using Roslynator.Testing.CSharp;
+using Xunit;
+
+namespace Roslynator.CSharp.Analysis.Tests;
+
+public class RCS1105UnnecessaryInterpolationTests : AbstractCSharpDiagnosticVerifier<UnnecessaryInterpolationAnalyzer, InterpolationCodeFixProvider>
+{
+    public override DiagnosticDescriptor Descriptor { get; } = DiagnosticRules.UnnecessaryInterpolation;
+
+    [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.UseVarOrExplicitType)]
+    public async Task TestNoDiagnostic_RawStringLiteral()
+    {
+        await VerifyNoDiagnosticAsync(""""
+class C
+{
+    void M()
+    {
+        var s = $"""a {"\n"} b""";
+    }
+}
+"""");
+    }
+}