From b979d41ec5d1a28658dafa1fb188dd51e52126b3 Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Sun, 30 Aug 2026 01:56:01 +0000
Subject: [PATCH 1/4] Fix ShapeTag generation to omit '?' suffix for
 non-blittable types

---
 src/ZeroSerializerGenerator.cs | 7 ++++++-
 tests/ShapeTagAndHashTests.cs  | 2 +-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/ZeroSerializerGenerator.cs b/src/ZeroSerializerGenerator.cs
index 53c9e9a..ab4dbf1 100644
--- a/src/ZeroSerializerGenerator.cs
+++ b/src/ZeroSerializerGenerator.cs
@@ -1736,7 +1736,12 @@ private static void CreateShapeTag(ITypeSymbol typeSymbol, StringBuilder shapeTa
         {
             var underlying = nullableType.TypeArguments[0];
             CreateShapeTag(underlying, shapeTagBuilder);
-            shapeTagBuilder.Append('?');
+            if (underlying is not INamedTypeSymbol namedUnderlying
+                || namedUnderlying.TypeKind != TypeKind.Struct
+                || TryGetBlittableStructByteCount(namedUnderlying, out _))
+            {
+                shapeTagBuilder.Append('?');
+            }
             return;
         }
 
diff --git a/tests/ShapeTagAndHashTests.cs b/tests/ShapeTagAndHashTests.cs
index 6a7e9bb..e2b07e5 100644
--- a/tests/ShapeTagAndHashTests.cs
+++ b/tests/ShapeTagAndHashTests.cs
@@ -48,7 +48,7 @@ public void EnumClassViewTest()
     [Fact]
     public void SchemaSignatureTestsModelViewTest()
     {
-        string schemaSignatureExpected = "v1/{blittable{int,enum:short},{int,enum:byte},blittable{int,enum:short}[],{},blittable{},{enum:byte,enum:short}?,enum:byte[],enum:ulong[],int?,bool?}";
+        string schemaSignatureExpected = "v1/{blittable{int,enum:short},{int,enum:byte},blittable{int,enum:short}[],{},blittable{},{enum:byte,enum:short},enum:byte[],enum:ulong[],int?,bool?}";
         Assert.Equal(SchemaSignatureTestsModelView.ShapeTag, schemaSignatureExpected);
         Assert.Equal(SchemaSignatureTestsModelView.ShapeHash, XXHash32.HashToUInt32(schemaSignatureExpected));
     }

From 47710296f450026c26ec96d00a8e88239bdc4547 Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Sun, 30 Aug 2026 02:07:06 +0000
Subject: [PATCH 2/4] Refactor ShapeTag nullable struct check to target
 blittable structs

---
 src/ZeroSerializerGenerator.cs | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/src/ZeroSerializerGenerator.cs b/src/ZeroSerializerGenerator.cs
index ab4dbf1..836f8d8 100644
--- a/src/ZeroSerializerGenerator.cs
+++ b/src/ZeroSerializerGenerator.cs
@@ -1736,9 +1736,14 @@ private static void CreateShapeTag(ITypeSymbol typeSymbol, StringBuilder shapeTa
         {
             var underlying = nullableType.TypeArguments[0];
             CreateShapeTag(underlying, shapeTagBuilder);
-            if (underlying is not INamedTypeSymbol namedUnderlying
-                || namedUnderlying.TypeKind != TypeKind.Struct
-                || TryGetBlittableStructByteCount(namedUnderlying, out _))
+            if (underlying is INamedTypeSymbol namedUnderlying && namedUnderlying.TypeKind == TypeKind.Struct)
+            {
+                if (TryGetBlittableStructByteCount(namedUnderlying, out _))
+                {
+                    shapeTagBuilder.Append('?');
+                }
+            }
+            else
             {
                 shapeTagBuilder.Append('?');
             }

From 12580ebca6be6a116097286862c0091f75180149 Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Sun, 30 Aug 2026 02:10:02 +0000
Subject: [PATCH 3/4] Refactor ShapeTag nullable check to explicitly detect
 non-blittable structs

---
 src/ZeroSerializerGenerator.cs | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/src/ZeroSerializerGenerator.cs b/src/ZeroSerializerGenerator.cs
index 836f8d8..3d46316 100644
--- a/src/ZeroSerializerGenerator.cs
+++ b/src/ZeroSerializerGenerator.cs
@@ -1736,14 +1736,7 @@ private static void CreateShapeTag(ITypeSymbol typeSymbol, StringBuilder shapeTa
         {
             var underlying = nullableType.TypeArguments[0];
             CreateShapeTag(underlying, shapeTagBuilder);
-            if (underlying is INamedTypeSymbol namedUnderlying && namedUnderlying.TypeKind == TypeKind.Struct)
-            {
-                if (TryGetBlittableStructByteCount(namedUnderlying, out _))
-                {
-                    shapeTagBuilder.Append('?');
-                }
-            }
-            else
+            if (!IsNonBlittableStruct(underlying))
             {
                 shapeTagBuilder.Append('?');
             }
@@ -1810,6 +1803,13 @@ private static void CreateShapeTag(ITypeSymbol typeSymbol, StringBuilder shapeTa
         shapeTagBuilder.Append(UnknownShapeTagType);
     }
 
+    private static bool IsNonBlittableStruct(ITypeSymbol typeSymbol)
+    {
+        return typeSymbol.TypeKind == TypeKind.Struct
+            && GetPrimitiveKeyword(typeSymbol).Length == 0
+            && !TryGetFixedTypeByteCount(typeSymbol, new HashSet<ITypeSymbol>(SymbolEqualityComparer.Default), out _);
+    }
+
     private static string GetPrimitiveKeyword(ITypeSymbol? typeSymbol)
     {
         return typeSymbol?.SpecialType switch

From 41801cc9ec7902c879e19a915717b8be21ea90c9 Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Sun, 30 Aug 2026 02:17:53 +0000
Subject: [PATCH 4/4] Simplify ShapeTag nullable check for non-blittable
 structs

---
 src/ZeroSerializerGenerator.cs | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/src/ZeroSerializerGenerator.cs b/src/ZeroSerializerGenerator.cs
index 3d46316..af0151e 100644
--- a/src/ZeroSerializerGenerator.cs
+++ b/src/ZeroSerializerGenerator.cs
@@ -1736,10 +1736,11 @@ private static void CreateShapeTag(ITypeSymbol typeSymbol, StringBuilder shapeTa
         {
             var underlying = nullableType.TypeArguments[0];
             CreateShapeTag(underlying, shapeTagBuilder);
-            if (!IsNonBlittableStruct(underlying))
+            if (underlying is INamedTypeSymbol named && named.TypeKind == TypeKind.Struct && !TryGetBlittableStructByteCount(named, out _))
             {
-                shapeTagBuilder.Append('?');
+                return;
             }
+            shapeTagBuilder.Append('?');
             return;
         }
 
@@ -1803,13 +1804,6 @@ private static void CreateShapeTag(ITypeSymbol typeSymbol, StringBuilder shapeTa
         shapeTagBuilder.Append(UnknownShapeTagType);
     }
 
-    private static bool IsNonBlittableStruct(ITypeSymbol typeSymbol)
-    {
-        return typeSymbol.TypeKind == TypeKind.Struct
-            && GetPrimitiveKeyword(typeSymbol).Length == 0
-            && !TryGetFixedTypeByteCount(typeSymbol, new HashSet<ITypeSymbol>(SymbolEqualityComparer.Default), out _);
-    }
-
     private static string GetPrimitiveKeyword(ITypeSymbol? typeSymbol)
     {
         return typeSymbol?.SpecialType switch