add: Template Define

src/Generators/RegistryEntityGenerator.cs

@@ -1,6 +1,7 @@
 using System.Linq;
 using System.Text;
 using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
 
 namespace Polonium.Generators.Generators;
 [Generator]
@@ -12,7 +13,7 @@ public class RegistryEntityGenerator : AssetProcessGenerator
             return;
         Compilation compilation = context.Compilation;
         INamedTypeSymbol? regEntity = compilation.GetTypeByMetadataName("Polonium.Attributes.RegistryEntity");
-        foreach (var derivedClassDeclaration in receiver.Classes)
+        foreach (ClassDeclarationSyntax? derivedClassDeclaration in receiver.Classes)
         {
             SemanticModel model = compilation.GetSemanticModel(derivedClassDeclaration.SyntaxTree);
             if (