From ef35e25e12717697de6cfe094174f0e950c75e7e Mon Sep 17 00:00:00 2001
From: Paul Braetz <paul.braetz@rhomicro.com>
Date: Sun, 4 Jan 2026 04:02:50 +0100
Subject: [PATCH 1/2] remove empty project

---
 .../CSharpSourceBuilder.TestApplication.csproj    | 15 ---------------
 CSharpSourceBuilder.TestApplication/Program.cs    |  4 ----
 RhoMicro.CodeAnalysis.slnx                        |  1 -
 3 files changed, 20 deletions(-)
 delete mode 100644 CSharpSourceBuilder.TestApplication/CSharpSourceBuilder.TestApplication.csproj
 delete mode 100644 CSharpSourceBuilder.TestApplication/Program.cs

diff --git a/CSharpSourceBuilder.TestApplication/CSharpSourceBuilder.TestApplication.csproj b/CSharpSourceBuilder.TestApplication/CSharpSourceBuilder.TestApplication.csproj
deleted file mode 100644
index 2fc683e..0000000
--- a/CSharpSourceBuilder.TestApplication/CSharpSourceBuilder.TestApplication.csproj
+++ /dev/null
@@ -1,15 +0,0 @@
-<Project Sdk="Microsoft.NET.Sdk">
-
-  <PropertyGroup>
-    <OutputType>Exe</OutputType>
-    <TargetFramework>net9.0</TargetFramework>
-    <LangVersion>preview</LangVersion>
-    <ImplicitUsings>enable</ImplicitUsings>
-    <Nullable>enable</Nullable>
-  </PropertyGroup>
-
-  <ItemGroup>
-    <ProjectReference Include="..\Lyra\Lyra.csproj" OutputItemType="analyzer" ReferenceOutputAssembly="false" />
-  </ItemGroup>
-
-</Project>
diff --git a/CSharpSourceBuilder.TestApplication/Program.cs b/CSharpSourceBuilder.TestApplication/Program.cs
deleted file mode 100644
index be6129a..0000000
--- a/CSharpSourceBuilder.TestApplication/Program.cs
+++ /dev/null
@@ -1,4 +0,0 @@
-// See https://aka.ms/new-console-template for more information
-
-using RhoMicro.CodeAnalysis;
-
diff --git a/RhoMicro.CodeAnalysis.slnx b/RhoMicro.CodeAnalysis.slnx
index 40817fd..bb16803 100644
--- a/RhoMicro.CodeAnalysis.slnx
+++ b/RhoMicro.CodeAnalysis.slnx
@@ -1,6 +1,5 @@
 <Solution>
   <Folder Name="/Applications/">
-    <Project Path="CSharpSourceBuilder.TestApplication\CSharpSourceBuilder.TestApplication.csproj" />
     <Project Path="DslGenerator.TestApp/DslGenerator.TestApp.csproj" />
     <Project Path="EnumStringTestApp/EnumStringTestApp.csproj" />
     <Project Path="IndentedStringBuilderTestApp/IndentedStringBuilderTestApp.csproj" />

From 366fd9f84a47085ff928f6d899be016c13cca7d0 Mon Sep 17 00:00:00 2001
From: Paul Braetz <paul.braetz@rhomicro.com>
Date: Sun, 4 Jan 2026 18:28:11 +0100
Subject: [PATCH 2/2] allow unmanaged union type variants

---
 .../Models/UnionTypeAttribute.Model.cs        | 86 ++++++++++++++++++-
 Janus.Tests.EndToEnd/UnionTypeVariantTest.cs  | 20 +++++
 2 files changed, 104 insertions(+), 2 deletions(-)
 create mode 100644 Janus.Tests.EndToEnd/UnionTypeVariantTest.cs

diff --git a/Janus.Analyzers/Models/UnionTypeAttribute.Model.cs b/Janus.Analyzers/Models/UnionTypeAttribute.Model.cs
index 66250d0..cf82d14 100644
--- a/Janus.Analyzers/Models/UnionTypeAttribute.Model.cs
+++ b/Janus.Analyzers/Models/UnionTypeAttribute.Model.cs
@@ -92,7 +92,7 @@ private void Initialize(ITypeSymbol variant, CancellationToken ct)
                 Type = new(
                     isArray
                         ? VariantTypeKind.Reference
-                        : actualVariant.IsUnmanagedType
+                        : actualVariant.IsUnmanagedOrUnmanagedUnionType
                             ? VariantTypeKind.Unmanaged
                             : VariantTypeKind.Value,
                     IsNullable: true,
@@ -106,7 +106,7 @@ private void Initialize(ITypeSymbol variant, CancellationToken ct)
                 var name = variant.ToDisplayString(TypeDisplayFormat);
                 Type = extractedVariant switch
                 {
-                    { IsUnmanagedType: true } =>
+                    { IsUnmanagedOrUnmanagedUnionType: true } =>
                         new(isArray
                                 ? VariantTypeKind.Reference
                                 : VariantTypeKind.Unmanaged,
@@ -172,3 +172,85 @@ public override Boolean IsNullable
         set => base.IsNullable = value;
     }
 }
+
+file static class Extensions
+{
+    extension(ITypeSymbol symbol)
+    {
+        public Boolean IsUnmanagedOrUnmanagedUnionType
+        {
+            get
+            {
+                var result = isUnmanaged(symbol, null);
+
+                return result;
+
+                Boolean isUnmanaged(ITypeSymbol candidate, Dictionary<ITypeSymbol, Boolean?>? unmanagedTypes)
+                {
+                    if (!candidate.IsUnmanagedType)
+                    {
+                        unmanagedTypes?[candidate] = false;
+                        return false;
+                    }
+
+                    unmanagedTypes = new Dictionary<ITypeSymbol, Boolean?>(SymbolEqualityComparer.Default);
+
+                    if (unmanagedTypes.TryGetValue(candidate, out var memoizedValue))
+                    {
+                        if (memoizedValue is { } memoizedResult)
+                        {
+                            return memoizedResult;
+                        }
+
+                        return true;
+                    }
+
+                    var typeAttributes = candidate.GetAttributes();
+                    foreach (var attribute in typeAttributes)
+                    {
+                        if (!attribute.IsUnionTypeAttribute())
+                        {
+                            continue;
+                        }
+
+                        foreach (var variant in attribute.AttributeClass?.TypeArguments ?? [])
+                        {
+                            if (isUnmanaged(variant, unmanagedTypes))
+                            {
+                                continue;
+                            }
+
+                            unmanagedTypes[candidate] = false;
+                            return false;
+                        }
+                    }
+
+                    if (candidate is INamedTypeSymbol namedCandidate)
+                    {
+                        foreach (var typeParameter in namedCandidate.TypeParameters)
+                        {
+                            if (typeParameter.HasUnmanagedTypeConstraint)
+                            {
+                                continue;
+                            }
+
+                            var typeParameterAttributes = typeParameter.GetAttributes();
+
+                            foreach (var attribute in typeParameterAttributes)
+                            {
+                                if (attribute.IsUnionTypeAttribute())
+                                {
+                                    unmanagedTypes[candidate] = false;
+                                    return false;
+                                }
+                            }
+                        }
+                    }
+
+                    unmanagedTypes[candidate] = true;
+                    return true;
+                }
+            }
+        }
+    }
+}
diff --git a/Janus.Tests.EndToEnd/UnionTypeVariantTest.cs b/Janus.Tests.EndToEnd/UnionTypeVariantTest.cs
new file mode 100644
index 0000000..f263b89
--- /dev/null
+++ b/Janus.Tests.EndToEnd/UnionTypeVariantTest.cs
@@ -0,0 +1,20 @@
+// SPDX-License-Identifier: MPL-2.0
+
+namespace RhoMicro.CodeAnalysis.Janus.EndToEnd.Tests;
+
+public partial class UnionTypeVariantTests
+{
+    [UnionType<String>]
+    partial struct Text;
+
+    [UnionType<Text, Int32>]
+    partial struct Union;
+
+    [Fact]
+    public void ManagedUnionTypeStructVariantDoesNotThrowTle()
+    {
+        Text text = "foo";
+        Union union = text;
+        Assert.Equal(text, union.CastToText);
+    }
+}