add a workaround

It's only required until dotnet/roslyn#71115 is fixed.

CodeConverter/CSharp/CommonConversions.cs

@@ -598,7 +598,7 @@ public CSSyntax.IdentifierNameSyntax GetRetVariableNameOrNull(VBSyntax.MethodBlo
             var flow = SemanticModel.AnalyzeDataFlow(node.Statements.First(), node.Statements.Last());
 
             if (flow.Succeeded) {
-                assignsToMethodNameVariable = flow.ReadInside.Any(equalsMethodName) || flow.WrittenInside.Any(equalsMethodName);
+                assignsToMethodNameVariable = flow.ReadInsideSafe().Any(equalsMethodName) || flow.WrittenInside.Any(equalsMethodName);
             }
         }
 

CodeConverter/CSharp/DataFlowAnalysisExtensions.cs

@@ -0,0 +1,24 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace ICSharpCode.CodeConverter.CSharp;
+internal static class DataFlowAnalysisExtensions
+{
+    /// <summary>
+    /// Accesses the <see cref="DataFlowAnalysis.ReadInside" /> second time in case of exception.
+    /// This is a workaround for a bug present in Roslyn up to version 4.8.0
+    /// (https://github.com/dotnet/roslyn/issues/71115)
+    /// </summary>
+    public static System.Collections.Immutable.ImmutableArray<ISymbol> ReadInsideSafe(this DataFlowAnalysis dataFlow)
+    {
+        try
+        {
+            return dataFlow.ReadInside;
+        }
+        catch
+        {
+            return dataFlow.ReadInside;
+        }
+    }
+}

CodeConverter/CSharp/DefiniteAssignmentAnalyzer.cs

@@ -5,7 +5,7 @@ internal static class DefiniteAssignmentAnalyzer
 
     public static bool IsDefinitelyAssignedBeforeRead(ISymbol localSymbol, DataFlowAnalysis methodFlow)
     {
-        if (!methodFlow.ReadInside.Contains(localSymbol)) return true;
+        if (!methodFlow.ReadInsideSafe().Contains(localSymbol)) return true;
         var unassignedVariables = methodFlow.GetVbUnassignedVariables();
         return unassignedVariables != null && !unassignedVariables.Contains(localSymbol, SymbolEqualityComparer.IncludeNullability);
     }