Fix RCS1197

src/Analyzers/CSharp/Analysis/OptimizeStringBuilderAppendCallAnalysis.cs

@@ -33,6 +33,9 @@ public static void Analyze(SyntaxNodeAnalysisContext context, in SimpleMemberInv
 
             SimpleMemberInvocationExpressionInfo invocationInfo2 = SyntaxInfo.SimpleMemberInvocationExpressionInfo(invocationInfo.Expression);
 
+            if (!invocationInfo2.Success)
+                return;
+
             if (invocationInfo2.NameText != "Append")
                 return;
 

src/Tests/Analyzers.Tests/RCS1197OptimizeStringBuilderAppendCallTests.cs

@@ -952,6 +952,25 @@ void M()
         var sb = new StringBuilder().Append($""{Foo}Bar"");
     }
 }
+");
+    }
+
+    [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.OptimizeStringBuilderAppendCall)]
+    public async Task TestNoDiagnostic_NoAppendMethodChain()
+    {
+        await VerifyNoDiagnosticAsync(@"
+using System.Text;
+
+class C
+{
+    string M()
+    {
+        var sb = new StringBuilder();
+        _ = sb.AppendLine();
+
+        return sb.ToString();
+    }
+}
 ");
     }
 }

src/VisualStudioCode/package/CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Fix [RCS1197](https://josefpihrt.github.io/docs/roslynator/analyzers/RCS1197) ([PR](https://github.com/dotnet/roslynator/pull/1226)).
+
 ## [4.6.0] - 2023-10-18
 
 ### Added