Avoid marshalling of instance data

src/Libs/GObject-2.0/Internal/ObjectWrapper.cs

@@ -1,7 +1,7 @@
 using System;
 using System.Diagnostics;
 using System.Reflection;
-using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
 using GLib;
 
 namespace GObject.Internal;
@@ -78,16 +78,15 @@ public static T WrapInterfaceHandle<T>(IntPtr handle, bool ownedRef) where T : c
         return (T) ctor.Invoke(new object[] { handle, ownedRef });
     }
 
-    private static Type GetTypeFromInstance(IntPtr handle)
+    private static unsafe Type GetTypeFromInstance(IntPtr handle)
     {
-        TypeInstanceData instance = Marshal.PtrToStructure<TypeInstanceData>(handle);
-        TypeClassData klass = Marshal.PtrToStructure<TypeClassData>(instance.GClass);
-        var typeid = klass.GType;
+        var gclass = Unsafe.AsRef<TypeInstanceData>((void*) handle).GClass;
+        var gtype = Unsafe.AsRef<TypeClassData>((void*) gclass).GType;
 
-        if (typeid == 0)
+        if (gtype == 0)
             throw new Exception("Could not retrieve type from class struct - is the struct valid?");
 
-        return new Type(typeid);
+        return new Type(gtype);
     }
 
     private static ConstructorInfo? GetObjectConstructor(System.Type type)

src/Native/GirTestLib/girtest-class-tester.c

@@ -34,3 +34,16 @@ girtest_class_tester_transfer_ownership_full_and_unref(GObject *object)
 {
     g_object_unref(object);
 }
+
+/**
+ * girtest_class_tester_create_hidden_instance:
+ *
+ * Creates a new `girtest_class_tester_new` disguised in a GObject.
+ *
+ * Returns: (transfer full): The newly created `girtest_class_tester` casted as GObject.
+ */
+GObject*
+girtest_class_tester_create_hidden_instance (void)
+{
+    return g_object_new (GIRTEST_TYPE_CLASS_TESTER, NULL);
+}

src/Native/GirTestLib/girtest-class-tester.h

@@ -11,5 +11,8 @@ G_DECLARE_FINAL_TYPE(GirTestClassTester, girtest_class_tester, GIRTEST, CLASS_TE
 void
 girtest_class_tester_transfer_ownership_full_and_unref(GObject *object);
 
+GObject*
+girtest_class_tester_create_hidden_instance (void);
+
 G_END_DECLS
 

src/Tests/Libs/GirTest-0.1.Tests/ClassTest.cs

@@ -30,6 +30,17 @@ public void InstanceIsGarbageCollectedAfterOwnershipTransferAndUnref()
         reference.IsAlive.Should().BeFalse();
     }
 
+    [TestMethod]
+    public void CanReturnHiddenInstance()
+    {
+        //Ensure that return type of "CreateHiddenInstance" is "GObject.Object"
+        typeof(ClassTester).GetMethod(nameof(ClassTester.CreateHiddenInstance)).Should().Return<GObject.Object>();
+
+        //Ensure that returned instance actually is a "ClassTester"
+        var instance = ClassTester.CreateHiddenInstance();
+        instance.Should().BeOfType<ClassTester>();
+    }
+
     private class TestClass : GObject.Object
     {
         public TestClass() : base(true, System.Array.Empty<GObject.ConstructArgument>()) { }