Update ZEROS007 diagnostic to recommend flags enum for bool properties

README.ja.md

@@ -73,7 +73,7 @@ Blittable Struct は全ケースで offset table を持たない raw payload と
 
 `[ZeroSerializer]` が付いていても Blittable Struct はネスト View 化しません。親が非 Blittable 型なら親の field offset table は存在しますが、Blittable Struct payload 内部には table を生成しません。
 
-全フィールド型が Blittable 対応済みで、自身の `StructLayout(LayoutKind.Sequential, Pack = 1)` だけが不足する `[ZeroSerializer]` struct には、型名 identifier へ `ZEROS006` warning を出します。その struct が有効な `[ZeroSerializer]` ネスト型として使われている場合は、raw payload 化による性能改善を案内する `ZEROS007` info もネスト型の identifier へ1回だけ出します。`[ZeroSerializer]` がない間は親型に `ZEROS003` error が発生し、`ZEROS007` は生成エラーが解消されるまで出ません。
+全フィールド型が Blittable 対応済みで、自身の `StructLayout(LayoutKind.Sequential, Pack = 1)` だけが不足する `[ZeroSerializer]` struct には、型名 identifier へ `ZEROS006` warning を出します。
 
 ネストした class/struct にも `[ZeroSerializer]` が必要です。未修飾の型は `ZEROS003` error になります。
 

src/ZeroSerializerGenerator.cs

@@ -76,10 +76,10 @@ public sealed class ZeroSerializerGenerator : ISourceGenerator
         DiagnosticSeverity.Warning,
         isEnabledByDefault: true);
 
-    private static readonly DiagnosticDescriptor BlittableCompatibleNestedStruct = new(
+    private static readonly DiagnosticDescriptor UseFlagsEnumToReducePayloadSize = new(
         "ZEROS007",
-        "Nested struct can use faster Blittable serialization",
-        "Nested struct '{0}' can use StructLayout(LayoutKind.Sequential, Pack = 1) to improve serialization performance with raw payload serialization",
+        "Use flags enum to reduce payload size",
+        "Property '{0}' uses bool type; consider using a flags enum (byte) to reduce payload size by combining up to 8 booleans into one byte",
         SerializerName,
         DiagnosticSeverity.Info,
         isEnabledByDefault: true);
@@ -249,11 +249,6 @@ private static void ExecuteCore(
             return;
         }
 
-        ReportBlittableCompatibleNestedStructDiagnostics(
-            executionContext,
-            validModels,
-            generationModels);
-
         var modelLookup = new Dictionary<INamedTypeSymbol, TypeGenerationModel>(SymbolEqualityComparer.Default);
         // Each type owns one generated file and contributes one method to its namespace-local partial extension class.
         foreach (TypeGenerationModel validModel in validModels)
@@ -373,6 +368,14 @@ private static TypeGenerationModel CreateGenerationModel(
                 continue;
             }
 
+            if (serializableProperty.Type.SpecialType == SpecialType.System_Boolean)
+            {
+                executionContext.ReportDiagnostic(Diagnostic.Create(
+                    UseFlagsEnumToReducePayloadSize,
+                    GetPropertyTypeLocation(serializableProperty),
+                    serializableProperty.Name));
+            }
+
             generationModel.Fields.Add(propertyModel);
         }
 
@@ -761,36 +764,6 @@ private static bool HasBlittableCompatibleFieldShape(INamedTypeSymbol candidateS
         return true;
     }
 
-    private static void ReportBlittableCompatibleNestedStructDiagnostics(
-        GeneratorExecutionContext executionContext,
-        IReadOnlyList<TypeGenerationModel> validGenerationModels,
-        IReadOnlyDictionary<INamedTypeSymbol, TypeGenerationModel> generationModels)
-    {
-        var reportedNestedStructs = new HashSet<INamedTypeSymbol>(SymbolEqualityComparer.Default);
-        foreach (TypeGenerationModel containingGenerationModel in validGenerationModels)
-        {
-            foreach (FieldGenerationModel nestedField in containingGenerationModel.Fields)
-            {
-                if (nestedField.Kind != FieldSerializationKind.Nested
-                    || nestedField.NestedSerializableType is not INamedTypeSymbol nestedSerializableStruct
-                    || nestedSerializableStruct.TypeKind != TypeKind.Struct
-                    || !generationModels.TryGetValue(nestedSerializableStruct, out TypeGenerationModel? nestedGenerationModel)
-                    || nestedGenerationModel.IsBlittableStruct
-                    || !HasBlittableCompatibleFieldShape(nestedSerializableStruct)
-                    || !reportedNestedStructs.Add(nestedSerializableStruct))
-                {
-                    continue;
-                }
-
-                // Report only after dependency validation so this performance advice never replaces ZEROS003 or another generation error.
-                executionContext.ReportDiagnostic(Diagnostic.Create(
-                    BlittableCompatibleNestedStruct,
-                    GetTypeIdentifierLocation(nestedSerializableStruct),
-                    nestedSerializableStruct.ToDisplayString()));
-            }
-        }
-    }
-
     private static Location? GetTypeIdentifierLocation(INamedTypeSymbol declaredType)
     {
         foreach (SyntaxReference declaringSyntaxReference in declaredType.DeclaringSyntaxReferences)

tests/Diagnostics/DiagnosticTests.cs

@@ -507,54 +507,37 @@ await CSharpSourceGeneratorVerifier<ZeroSerializerGenerator>.VerifySourceGenerat
     }
 
     [Fact]
-    public async Task ZEROS007_Violation_BlittableCompatibleNestedStruct()
+    public async Task ZEROS007_Violation_BoolProperty()
     {
         string source = @"
 using ZeroSerializer;
 
 [ZeroSerializer]
-public struct {|#0:NestedStruct|}
+public class MyBoolClass
 {
-    public int Value { get; set; }
-}
-
-[ZeroSerializer]
-public class ParentClass
-{
-    public NestedStruct Child { get; set; }
+    public {|#0:bool|} IsActive { get; set; }
 }
 ";
 
         await CSharpSourceGeneratorVerifier<ZeroSerializerGenerator>.VerifySourceGeneratorAsync(
             source,
-            new DiagnosticResult("ZEROS006", DiagnosticSeverity.Warning)
-                .WithLocation(0)
-                .WithMessage("Struct 'NestedStruct' has a Blittable-compatible field shape; use StructLayout(LayoutKind.Sequential, Pack = 1) to enable raw payload serialization"),
             new DiagnosticResult("ZEROS007", DiagnosticSeverity.Info)
                 .WithLocation(0)
-                .WithMessage("Nested struct 'NestedStruct' can use StructLayout(LayoutKind.Sequential, Pack = 1) to improve serialization performance with raw payload serialization")
+                .WithMessage("Property 'IsActive' uses bool type; consider using a flags enum (byte) to reduce payload size by combining up to 8 booleans into one byte")
         );
     }
 
     [Fact]
-    public async Task ZEROS007_Compliant_BlittableNestedStructWithLayout()
+    public async Task ZEROS007_Compliant_NonBoolProperty()
     {
         string source = @"
-using System.Runtime.InteropServices;
 using ZeroSerializer;
 
 [ZeroSerializer]
-[StructLayout(LayoutKind.Sequential, Pack = 1)]
-public struct NestedStructWithLayout
+public class MyNonBoolClass
 {
     public int Value { get; set; }
 }
-
-[ZeroSerializer]
-public class ParentClassWithBlittable
-{
-    public NestedStructWithLayout Child { get; set; }
-}
 ";
 
         await CSharpSourceGeneratorVerifier<ZeroSerializerGenerator>.VerifySourceGeneratorAsync(