Generate syntax lists with the correct type

Author: sharwell

src/NetAnalyzers/CSharp/Microsoft.NetCore.Analyzers/InteropServices/CSharpDynamicInterfaceCastableImplementation.Fixer.cs

@@ -163,8 +163,8 @@ private static SyntaxNode GenerateEventImplementation(
                     SyntaxFactory.List(
                 new[]
                 {
-                        generator.WithStatements(generator.GetAccessor(eventDeclaration, DeclarationKind.AddAccessor), defaultMethodBodyStatements),
-                        generator.WithStatements(generator.GetAccessor(eventDeclaration, DeclarationKind.RemoveAccessor), defaultMethodBodyStatements),
+                        (AccessorDeclarationSyntax)generator.WithStatements(generator.GetAccessor(eventDeclaration, DeclarationKind.AddAccessor), defaultMethodBodyStatements),
+                        (AccessorDeclarationSyntax)generator.WithStatements(generator.GetAccessor(eventDeclaration, DeclarationKind.RemoveAccessor), defaultMethodBodyStatements),
                 })));
         }
 
@@ -249,7 +249,7 @@ protected override async Task<Document> MakeMemberDeclaredOnImplementationTypeSt
                         var currentInvocation = (InvocationExpressionSyntax)node;
 
                         var newArgList = currentInvocation.ArgumentList.WithArguments(
-                            SyntaxFactory.SingletonSeparatedList(generator.Argument(invocation.target))
+                            SyntaxFactory.SingletonSeparatedList((ArgumentSyntax)generator.Argument(invocation.target))
                                 .AddRange(currentInvocation.ArgumentList.Arguments));
                         return currentInvocation.WithArgumentList(newArgList).WithExpression(SyntaxFactory.IdentifierName(symbol.Name));
                     });