VB -> C#: private partial methods do not compile

CodeConverter/CSharp/DeclarationNodeVisitor.cs

@@ -655,7 +655,7 @@ public override async Task<CSharpSyntaxNode> VisitMethodBlock(VBSyntax.MethodBlo
         var methodBlock = await node.SubOrFunctionStatement.AcceptAsync<BaseMethodDeclarationSyntax>(TriviaConvertingDeclarationVisitor, SourceTriviaMapKind.SubNodesOnly);
 
         var declaredSymbol = ModelExtensions.GetDeclaredSymbol(_semanticModel, node);
-        if (!declaredSymbol.CanHaveMethodBody()) {
+        if (declaredSymbol?.CanHaveMethodBody() == false) {
             return methodBlock;
         }
         var csReturnVariableOrNull = CommonConversions.GetRetVariableNameOrNull(node);
@@ -786,7 +786,8 @@ public override async Task<CSharpSyntaxNode> VisitMethodStatement(VBSyntax.Metho
             null
         );
 
-        return hasBody && declaredSymbol.CanHaveMethodBody() ? decl : decl.WithSemicolonToken(SemicolonToken);
+        bool canHaveMethodBody = declaredSymbol?.CanHaveMethodBody() != false;
+        return hasBody && canHaveMethodBody ? decl : decl.WithSemicolonToken(SemicolonToken);
     }
 
     public override async Task<CSharpSyntaxNode> VisitEventBlock(VBSyntax.EventBlockSyntax node)

CodeConverter/Util/ISymbolExtensions.cs

@@ -1,3 +1,4 @@
+#nullable enable
 namespace ICSharpCode.CodeConverter.Util;
 
 internal static class ISymbolExtensions
@@ -18,12 +19,9 @@ public static ISymbol GetBaseSymbol(this ISymbol symbol, Func<ISymbol, bool> sel
             : symbol;
     }
 
-    public static bool IsDefinedInSource(this ISymbol symbol)
-    {
-        return symbol.Locations.Any(loc => loc.IsInSource);
-    }
+    public static bool IsDefinedInSource(this ISymbol symbol) => symbol.Locations.Any(loc => loc.IsInSource);
 
-    public static TSymbol ExtractBestMatch<TSymbol>(this SymbolInfo info, Func<TSymbol, bool> isMatch = null) where TSymbol : class, ISymbol
+    public static TSymbol? ExtractBestMatch<TSymbol>(this SymbolInfo info, Func<TSymbol, bool>? isMatch = null) where TSymbol : class, ISymbol
     {
         isMatch ??= (_ => true);
         if (info.Symbol == null && info.CandidateSymbols.Length == 0)
@@ -38,16 +36,16 @@ public static TSymbol ExtractBestMatch<TSymbol>(this SymbolInfo info, Func<TSymb
         return null;
     }
 
-    public static string ToCSharpDisplayString(this ISymbol symbol, SymbolDisplayFormat format = null)
+    public static string? ToCSharpDisplayString(this ISymbol symbol, SymbolDisplayFormat? format = null)
     {
         if (TryGetSpecialVBTypeConversion(symbol, out var cSharpDisplayString)) return cSharpDisplayString;
 
         return symbol.ToDisplayString(format);
     }
 
-    private static bool TryGetSpecialVBTypeConversion(ISymbol symbol, out string cSharpDisplayString)
+    private static bool TryGetSpecialVBTypeConversion(ISymbol symbol, out string? cSharpDisplayString)
     {
-        var containingNamespace = symbol?.ContainingNamespace?.ToDisplayString(SymbolDisplayFormat.CSharpErrorMessageFormat);
+        var containingNamespace = symbol.ContainingNamespace?.ToDisplayString(SymbolDisplayFormat.CSharpErrorMessageFormat);
         if (containingNamespace == "Microsoft.VisualBasic" || containingNamespace == "System") {
             if (symbol is ITypeSymbol && TypesToConvertToDateTime.Contains(symbol.Name)) {
                 {
@@ -68,35 +66,28 @@ private static bool TryGetSpecialVBTypeConversion(ISymbol symbol, out string cSh
         return false;
     }
 
-    public static bool IsPartialMethodImplementation(this ISymbol declaredSymbol)
-    {
-        return declaredSymbol is IMethodSymbol ms && ms.PartialDefinitionPart != null;
-    }
+    public static bool IsPartialMethodImplementation(this ISymbol? declaredSymbol) =>
+        declaredSymbol is IMethodSymbol {PartialDefinitionPart: not null};
 
-    public static bool CanHaveMethodBody(this ISymbol declaredSymbol)
-    {
-        return !(declaredSymbol is IMethodSymbol ms) || ms.PartialImplementationPart == null && !ms.IsExtern;
-    }
+    public static bool CanHaveMethodBody(this ISymbol? declaredSymbol) =>
+        declaredSymbol is IMethodSymbol {IsExtern: false} && !IsPartialMethodDefinition(declaredSymbol);
 
-    public static bool IsPartialMethodDefinition(this ISymbol declaredSymbol)
-    {
-        return declaredSymbol is IMethodSymbol ms && ms.PartialImplementationPart != null;
-    }
+    public static bool IsPartialMethodDefinition(this ISymbol? declaredSymbol) =>
+        declaredSymbol is IMethodSymbol {PartialImplementationPart: not null}
+            or IMethodSymbol {IsPartialDefinition: true};
 
-    public static bool IsPartialClassDefinition(this ISymbol declaredSymbol)
+    public static bool IsPartialClassDefinition(this ISymbol? declaredSymbol)
     {
-        return declaredSymbol is ITypeSymbol ts && (ts.DeclaringSyntaxReferences.Length > 1
-                                                    || ts.ContainingAssembly.Name == ForcePartialTypesAssemblyName);
+        return declaredSymbol is ITypeSymbol {DeclaringSyntaxReferences.Length: > 1}
+            or ITypeSymbol {ContainingAssembly.Name: ForcePartialTypesAssemblyName};
     }
 
-    public static bool IsReducedTypeParameterMethod(this ISymbol symbol)
-    {
-        return symbol is IMethodSymbol ms && ms.ReducedFrom?.TypeParameters.Length > ms.TypeParameters.Length;
-    }
+    public static bool IsReducedTypeParameterMethod(this ISymbol? symbol) =>
+        symbol is IMethodSymbol ms && ms.ReducedFrom?.TypeParameters.Length > ms.TypeParameters.Length;
 
     /// <summary>
     /// Since non value types can't be ref types for extension methods in C#, convert to a static invocation
     /// https://github.com/icsharpcode/CodeConverter/issues/785
     /// </summary>
-    public static bool ValidCSharpExtensionMethodParameter(this IParameterSymbol vbSymbol) => vbSymbol != null && (vbSymbol.RefKind != RefKind.Ref || vbSymbol.Type.IsValueType);
+    public static bool ValidCSharpExtensionMethodParameter(this IParameterSymbol? vbSymbol) => vbSymbol != null && (vbSymbol.RefKind != RefKind.Ref || vbSymbol.Type.IsValueType);
 }

Tests/CSharp/MemberTests/MemberTests.cs

@@ -921,6 +921,13 @@ public partial class TestClass // VB doesn't require partial here (when just a s
 }");
     }
 
+    [Fact]
+    public async Task Issue1097_PartialMethodAsync()
+    {
+        await TestConversionVisualBasicToCSharpAsync(@"Partial Private Sub DummyMethod()
+    End Sub", @"partial void DummyMethod();");
+    }
+
     [Fact]
     public async Task NestedClassAsync()
     {