C#: Replace most conversions between Variant and System.Object

This commit replaces most usages of `ConvertManagedObjectToVariant` and
`ConvertVariantToManagedObjectOfType`, by using the `Godot.Variant`
struct instead of `System.Object`.

The most notable change is to the `GetGodotPropertyDefaultValues` method
that's generated for scripts. The dictionary it returns now stores
`Godot.Variant` values.

Remaining usages are:

- The `DelegateUtils` class, for the serialization of closure display
  classes during assembly reloading by the editor. These display classes
  are compiler generated classes to store values captured by a closure.
  Since it's generated by the compiler, the only way we have to access
  the fields is through reflection. This leads to using `System.Object`.
- Converting parameters when invoking constructors from the engine.
  This will be replaced with source generators in the future.
- Legacy support for old `GetGodotPropertyDefaultValues` return values.
  We need to keep supporting the old version of this generated method
  for some time. Otherwise, if loading a project built with the previous
  version, it could lead to the loss of exported property values.
  Ideally, we should remove this legacy support before a stable release.

4 files changed, 325 insertions, 423 deletions

diff --git a/modules/mono/glue/GodotSharp/GodotSharp/Core/Bridge/ScriptManagerBridge.cs b/modules/mono/glue/GodotSharp/GodotSharp/Core/Bridge/ScriptManagerBridge.cs
index d6fad391b6..e6a8054ae2 100644
--- a/modules/mono/glue/GodotSharp/GodotSharp/Core/Bridge/ScriptManagerBridge.cs
+++ b/modules/mono/glue/GodotSharp/GodotSharp/Core/Bridge/ScriptManagerBridge.cs
@@ -159,7 +159,7 @@ namespace Godot.Bridge
 
                 for (int i = 0; i < paramCount; i++)
                 {
-                    invokeParams[i] = Marshaling.ConvertVariantToManagedObjectOfType(
+                    invokeParams[i] = DelegateUtils.RuntimeTypeConversionHelper.ConvertToObjectOfType(
                         *args[i], parameters[i].ParameterType);
                 }
 
@@ -832,7 +832,8 @@ namespace Godot.Bridge
                 }
                 else
                 {
-                    interopProperties = ((godotsharp_property_info*)NativeMemory.Alloc((nuint)length, (nuint)sizeof(godotsharp_property_info)))!;
+                    interopProperties = ((godotsharp_property_info*)NativeMemory.Alloc(
+                        (nuint)length, (nuint)sizeof(godotsharp_property_info)))!;
                 }
 
                 try
@@ -858,8 +859,8 @@ namespace Godot.Bridge
 
                     addPropInfoFunc(scriptPtr, &currentClassName, interopProperties, length);
 
-                    // We're borrowing the StringName's without making an owning copy, so the
-                    // managed collection needs to be kept alive until `addPropInfoFunc` returns.
+                    // We're borrowing the native value of the StringName entries.
+                    // The dictionary needs to be kept alive until `addPropInfoFunc` returns.
                     GC.KeepAlive(properties);
                 }
                 finally
@@ -884,12 +885,7 @@ namespace Godot.Bridge
         {
             // Careful with padding...
             public godot_string_name Name; // Not owned
-            public godot_variant Value;
-
-            public void Dispose()
-            {
-                Value.Dispose();
-            }
+            public godot_variant Value; // Not owned
         }
 
         [UnmanagedCallersOnly]
@@ -928,10 +924,35 @@ namespace Godot.Bridge
                 if (getGodotPropertyDefaultValuesMethod == null)
                     return;
 
-                var defaultValues = (Dictionary<StringName, object>?)
-                    getGodotPropertyDefaultValuesMethod.Invoke(null, null);
+                var defaultValuesObj = getGodotPropertyDefaultValuesMethod.Invoke(null, null);
+
+                if (defaultValuesObj == null)
+                    return;
+
+                Dictionary<StringName, Variant> defaultValues;
+
+                if (defaultValuesObj is Dictionary<StringName, object> defaultValuesLegacy)
+                {
+                    // We have to support this for some time, otherwise this could cause data loss for projects
+                    // built with previous releases. Ideally, we should remove this before Godot 4.0 stable.
+
+                    if (defaultValuesLegacy.Count <= 0)
+                        return;
 
-                if (defaultValues == null || defaultValues.Count <= 0)
+                    defaultValues = new();
+
+                    foreach (var pair in defaultValuesLegacy)
+                    {
+                        defaultValues[pair.Key] = Variant.CreateTakingOwnershipOfDisposableValue(
+                            DelegateUtils.RuntimeTypeConversionHelper.ConvertToVariant(pair.Value));
+                    }
+                }
+                else
+                {
+                    defaultValues = (Dictionary<StringName, Variant>)defaultValuesObj;
+                }
+
+                if (defaultValues.Count <= 0)
                     return;
 
                 int length = defaultValues.Count;
@@ -952,7 +973,8 @@ namespace Godot.Bridge
                 }
                 else
                 {
-                    interopDefaultValues = ((godotsharp_property_def_val_pair*)NativeMemory.Alloc((nuint)length, (nuint)sizeof(godotsharp_property_def_val_pair)))!;
+                    interopDefaultValues = ((godotsharp_property_def_val_pair*)NativeMemory.Alloc(
+                        (nuint)length, (nuint)sizeof(godotsharp_property_def_val_pair)))!;
                 }
 
                 try
@@ -963,7 +985,7 @@ namespace Godot.Bridge
                         godotsharp_property_def_val_pair interopProperty = new()
                         {
                             Name = (godot_string_name)defaultValuePair.Key.NativeValue, // Not owned
-                            Value = Marshaling.ConvertManagedObjectToVariant(defaultValuePair.Value)
+                            Value = (godot_variant)defaultValuePair.Value.NativeVar // Not owned
                         };
 
                         interopDefaultValues[i] = interopProperty;
@@ -973,15 +995,12 @@ namespace Godot.Bridge
 
                     addDefValFunc(scriptPtr, interopDefaultValues, length);
 
-                    // We're borrowing the StringName's without making an owning copy, so the
-                    // managed collection needs to be kept alive until `addDefValFunc` returns.
+                    // We're borrowing the native value of the StringName and Variant entries.
+                    // The dictionary needs to be kept alive until `addDefValFunc` returns.
                     GC.KeepAlive(defaultValues);
                 }
                 finally
                 {
-                    for (int i = 0; i < length; i++)
-                        interopDefaultValues[i].Dispose();
-
                     if (!useStack)
                         NativeMemory.Free(interopDefaultValues);
                 }
diff --git a/modules/mono/glue/GodotSharp/GodotSharp/Core/DelegateUtils.cs b/modules/mono/glue/GodotSharp/GodotSharp/Core/DelegateUtils.cs
index d19e0c08f2..a3cfecfaa6 100644
--- a/modules/mono/glue/GodotSharp/GodotSharp/Core/DelegateUtils.cs
+++ b/modules/mono/glue/GodotSharp/GodotSharp/Core/DelegateUtils.cs
@@ -186,7 +186,7 @@ namespace Godot
                                 writer.Write(field.Name);
 
                                 var fieldValue = field.GetValue(target);
-                                using var fieldValueVariant = Marshaling.ConvertManagedObjectToVariant(fieldValue);
+                                using var fieldValueVariant = RuntimeTypeConversionHelper.ConvertToVariant(fieldValue);
                                 byte[] valueBuffer = VarToBytes(fieldValueVariant);
                                 writer.Write(valueBuffer.Length);
                                 writer.Write(valueBuffer);
@@ -443,7 +443,14 @@ namespace Godot
 
                             FieldInfo? fieldInfo = targetType.GetField(name,
                                 BindingFlags.Instance | BindingFlags.Public);
-                            fieldInfo?.SetValue(recreatedTarget, GD.BytesToVar(valueBuffer));
+
+                            if (fieldInfo != null)
+                            {
+                                var variantValue = GD.BytesToVar(valueBuffer);
+                                object? managedValue = RuntimeTypeConversionHelper.ConvertToObjectOfType(
+                                    (godot_variant)variantValue.NativeVar, fieldInfo.FieldType);
+                                fieldInfo.SetValue(recreatedTarget, managedValue);
+                            }
                         }
 
                         @delegate = Delegate.CreateDelegate(delegateType, recreatedTarget, methodInfo,
@@ -537,5 +544,269 @@ namespace Godot
 
             return type;
         }
+
+        internal static class RuntimeTypeConversionHelper
+        {
+            [SuppressMessage("ReSharper", "RedundantNameQualifier")]
+            public static godot_variant ConvertToVariant(object? obj)
+            {
+                if (obj == null)
+                    return default;
+
+                switch (obj)
+                {
+                    case bool @bool:
+                        return VariantUtils.CreateFrom(@bool);
+                    case char @char:
+                        return VariantUtils.CreateFrom(@char);
+                    case sbyte int8:
+                        return VariantUtils.CreateFrom(int8);
+                    case short int16:
+                        return VariantUtils.CreateFrom(int16);
+                    case int int32:
+                        return VariantUtils.CreateFrom(int32);
+                    case long int64:
+                        return VariantUtils.CreateFrom(int64);
+                    case byte uint8:
+                        return VariantUtils.CreateFrom(uint8);
+                    case ushort uint16:
+                        return VariantUtils.CreateFrom(uint16);
+                    case uint uint32:
+                        return VariantUtils.CreateFrom(uint32);
+                    case ulong uint64:
+                        return VariantUtils.CreateFrom(uint64);
+                    case float @float:
+                        return VariantUtils.CreateFrom(@float);
+                    case double @double:
+                        return VariantUtils.CreateFrom(@double);
+                    case Vector2 vector2:
+                        return VariantUtils.CreateFrom(vector2);
+                    case Vector2i vector2I:
+                        return VariantUtils.CreateFrom(vector2I);
+                    case Rect2 rect2:
+                        return VariantUtils.CreateFrom(rect2);
+                    case Rect2i rect2I:
+                        return VariantUtils.CreateFrom(rect2I);
+                    case Transform2D transform2D:
+                        return VariantUtils.CreateFrom(transform2D);
+                    case Vector3 vector3:
+                        return VariantUtils.CreateFrom(vector3);
+                    case Vector3i vector3I:
+                        return VariantUtils.CreateFrom(vector3I);
+                    case Vector4 vector4:
+                        return VariantUtils.CreateFrom(vector4);
+                    case Vector4i vector4I:
+                        return VariantUtils.CreateFrom(vector4I);
+                    case Basis basis:
+                        return VariantUtils.CreateFrom(basis);
+                    case Quaternion quaternion:
+                        return VariantUtils.CreateFrom(quaternion);
+                    case Transform3D transform3d:
+                        return VariantUtils.CreateFrom(transform3d);
+                    case Projection projection:
+                        return VariantUtils.CreateFrom(projection);
+                    case AABB aabb:
+                        return VariantUtils.CreateFrom(aabb);
+                    case Color color:
+                        return VariantUtils.CreateFrom(color);
+                    case Plane plane:
+                        return VariantUtils.CreateFrom(plane);
+                    case Callable callable:
+                        return VariantUtils.CreateFrom(callable);
+                    case SignalInfo signalInfo:
+                        return VariantUtils.CreateFrom(signalInfo);
+                    case string @string:
+                        return VariantUtils.CreateFrom(@string);
+                    case byte[] byteArray:
+                        return VariantUtils.CreateFrom(byteArray);
+                    case int[] int32Array:
+                        return VariantUtils.CreateFrom(int32Array);
+                    case long[] int64Array:
+                        return VariantUtils.CreateFrom(int64Array);
+                    case float[] floatArray:
+                        return VariantUtils.CreateFrom(floatArray);
+                    case double[] doubleArray:
+                        return VariantUtils.CreateFrom(doubleArray);
+                    case string[] stringArray:
+                        return VariantUtils.CreateFrom(stringArray);
+                    case Vector2[] vector2Array:
+                        return VariantUtils.CreateFrom(vector2Array);
+                    case Vector3[] vector3Array:
+                        return VariantUtils.CreateFrom(vector3Array);
+                    case Color[] colorArray:
+                        return VariantUtils.CreateFrom(colorArray);
+                    case StringName[] stringNameArray:
+                        return VariantUtils.CreateFrom(stringNameArray);
+                    case NodePath[] nodePathArray:
+                        return VariantUtils.CreateFrom(nodePathArray);
+                    case RID[] ridArray:
+                        return VariantUtils.CreateFrom(ridArray);
+                    case Godot.Object[] godotObjectArray:
+                        return VariantUtils.CreateFrom(godotObjectArray);
+                    case StringName stringName:
+                        return VariantUtils.CreateFrom(stringName);
+                    case NodePath nodePath:
+                        return VariantUtils.CreateFrom(nodePath);
+                    case RID rid:
+                        return VariantUtils.CreateFrom(rid);
+                    case Collections.Dictionary godotDictionary:
+                        return VariantUtils.CreateFrom(godotDictionary);
+                    case Collections.Array godotArray:
+                        return VariantUtils.CreateFrom(godotArray);
+                    case Variant variant:
+                        return VariantUtils.CreateFrom(variant);
+                    case Godot.Object godotObject:
+                        return VariantUtils.CreateFrom(godotObject);
+                    case Enum @enum:
+                        return VariantUtils.CreateFrom(Convert.ToInt64(@enum));
+                    case Collections.IGenericGodotDictionary godotDictionary:
+                        return VariantUtils.CreateFrom(godotDictionary.UnderlyingDictionary);
+                    case Collections.IGenericGodotArray godotArray:
+                        return VariantUtils.CreateFrom(godotArray.UnderlyingArray);
+                }
+
+                GD.PushError("Attempted to convert an unmarshallable managed type to Variant. Name: '" +
+                             obj.GetType().FullName + ".");
+                return new godot_variant();
+            }
+
+            private delegate object? ConvertToSystemObjectFunc(in godot_variant managed);
+
+            [SuppressMessage("ReSharper", "RedundantNameQualifier")]
+            // ReSharper disable once RedundantNameQualifier
+            private static readonly System.Collections.Generic.Dictionary<Type, ConvertToSystemObjectFunc>
+                ToSystemObjectFuncByType = new()
+                {
+                    [typeof(bool)] = (in godot_variant variant) => VariantUtils.ConvertTo<bool>(variant),
+                    [typeof(char)] = (in godot_variant variant) => VariantUtils.ConvertTo<char>(variant),
+                    [typeof(sbyte)] = (in godot_variant variant) => VariantUtils.ConvertTo<sbyte>(variant),
+                    [typeof(short)] = (in godot_variant variant) => VariantUtils.ConvertTo<short>(variant),
+                    [typeof(int)] = (in godot_variant variant) => VariantUtils.ConvertTo<int>(variant),
+                    [typeof(long)] = (in godot_variant variant) => VariantUtils.ConvertTo<long>(variant),
+                    [typeof(byte)] = (in godot_variant variant) => VariantUtils.ConvertTo<byte>(variant),
+                    [typeof(ushort)] = (in godot_variant variant) => VariantUtils.ConvertTo<ushort>(variant),
+                    [typeof(uint)] = (in godot_variant variant) => VariantUtils.ConvertTo<uint>(variant),
+                    [typeof(ulong)] = (in godot_variant variant) => VariantUtils.ConvertTo<ulong>(variant),
+                    [typeof(float)] = (in godot_variant variant) => VariantUtils.ConvertTo<float>(variant),
+                    [typeof(double)] = (in godot_variant variant) => VariantUtils.ConvertTo<double>(variant),
+                    [typeof(Vector2)] = (in godot_variant variant) => VariantUtils.ConvertTo<Vector2>(variant),
+                    [typeof(Vector2i)] = (in godot_variant variant) => VariantUtils.ConvertTo<Vector2i>(variant),
+                    [typeof(Rect2)] = (in godot_variant variant) => VariantUtils.ConvertTo<Rect2>(variant),
+                    [typeof(Rect2i)] = (in godot_variant variant) => VariantUtils.ConvertTo<Rect2i>(variant),
+                    [typeof(Transform2D)] = (in godot_variant variant) => VariantUtils.ConvertTo<Transform2D>(variant),
+                    [typeof(Vector3)] = (in godot_variant variant) => VariantUtils.ConvertTo<Vector3>(variant),
+                    [typeof(Vector3i)] = (in godot_variant variant) => VariantUtils.ConvertTo<Vector3i>(variant),
+                    [typeof(Basis)] = (in godot_variant variant) => VariantUtils.ConvertTo<Basis>(variant),
+                    [typeof(Quaternion)] = (in godot_variant variant) => VariantUtils.ConvertTo<Quaternion>(variant),
+                    [typeof(Transform3D)] = (in godot_variant variant) => VariantUtils.ConvertTo<Transform3D>(variant),
+                    [typeof(Vector4)] = (in godot_variant variant) => VariantUtils.ConvertTo<Vector4>(variant),
+                    [typeof(Vector4i)] = (in godot_variant variant) => VariantUtils.ConvertTo<Vector4i>(variant),
+                    [typeof(AABB)] = (in godot_variant variant) => VariantUtils.ConvertTo<AABB>(variant),
+                    [typeof(Color)] = (in godot_variant variant) => VariantUtils.ConvertTo<Color>(variant),
+                    [typeof(Plane)] = (in godot_variant variant) => VariantUtils.ConvertTo<Plane>(variant),
+                    [typeof(Callable)] = (in godot_variant variant) => VariantUtils.ConvertTo<Callable>(variant),
+                    [typeof(SignalInfo)] = (in godot_variant variant) => VariantUtils.ConvertTo<SignalInfo>(variant),
+                    [typeof(string)] = (in godot_variant variant) => VariantUtils.ConvertTo<string>(variant),
+                    [typeof(byte[])] = (in godot_variant variant) => VariantUtils.ConvertTo<byte[]>(variant),
+                    [typeof(int[])] = (in godot_variant variant) => VariantUtils.ConvertTo<int[]>(variant),
+                    [typeof(long[])] = (in godot_variant variant) => VariantUtils.ConvertTo<long[]>(variant),
+                    [typeof(float[])] = (in godot_variant variant) => VariantUtils.ConvertTo<float[]>(variant),
+                    [typeof(double[])] = (in godot_variant variant) => VariantUtils.ConvertTo<double[]>(variant),
+                    [typeof(string[])] = (in godot_variant variant) => VariantUtils.ConvertTo<string[]>(variant),
+                    [typeof(Vector2[])] = (in godot_variant variant) => VariantUtils.ConvertTo<Vector2[]>(variant),
+                    [typeof(Vector3[])] = (in godot_variant variant) => VariantUtils.ConvertTo<Vector3[]>(variant),
+                    [typeof(Color[])] = (in godot_variant variant) => VariantUtils.ConvertTo<Color[]>(variant),
+                    [typeof(StringName[])] =
+                        (in godot_variant variant) => VariantUtils.ConvertTo<StringName[]>(variant),
+                    [typeof(NodePath[])] = (in godot_variant variant) => VariantUtils.ConvertTo<NodePath[]>(variant),
+                    [typeof(RID[])] = (in godot_variant variant) => VariantUtils.ConvertTo<RID[]>(variant),
+                    [typeof(StringName)] = (in godot_variant variant) => VariantUtils.ConvertTo<StringName>(variant),
+                    [typeof(NodePath)] = (in godot_variant variant) => VariantUtils.ConvertTo<NodePath>(variant),
+                    [typeof(RID)] = (in godot_variant variant) => VariantUtils.ConvertTo<RID>(variant),
+                    [typeof(Godot.Collections.Dictionary)] = (in godot_variant variant) =>
+                        VariantUtils.ConvertTo<Godot.Collections.Dictionary>(variant),
+                    [typeof(Godot.Collections.Array)] =
+                        (in godot_variant variant) => VariantUtils.ConvertTo<Godot.Collections.Array>(variant),
+                    [typeof(Variant)] = (in godot_variant variant) => VariantUtils.ConvertTo<Variant>(variant),
+                };
+
+            [SuppressMessage("ReSharper", "RedundantNameQualifier")]
+            public static object? ConvertToObjectOfType(in godot_variant variant, Type type)
+            {
+                if (ToSystemObjectFuncByType.TryGetValue(type, out var func))
+                    return func(variant);
+
+                if (typeof(Godot.Object).IsAssignableFrom(type))
+                    return Convert.ChangeType(VariantUtils.ConvertTo<Godot.Object>(variant), type);
+
+                if (type.IsEnum)
+                {
+                    var enumUnderlyingType = type.GetEnumUnderlyingType();
+
+                    switch (Type.GetTypeCode(enumUnderlyingType))
+                    {
+                        case TypeCode.SByte:
+                            return Enum.ToObject(type, VariantUtils.ConvertToInt8(variant));
+                        case TypeCode.Int16:
+                            return Enum.ToObject(type, VariantUtils.ConvertToInt16(variant));
+                        case TypeCode.Int32:
+                            return Enum.ToObject(type, VariantUtils.ConvertToInt32(variant));
+                        case TypeCode.Int64:
+                            return Enum.ToObject(type, VariantUtils.ConvertToInt64(variant));
+                        case TypeCode.Byte:
+                            return Enum.ToObject(type, VariantUtils.ConvertToUInt8(variant));
+                        case TypeCode.UInt16:
+                            return Enum.ToObject(type, VariantUtils.ConvertToUInt16(variant));
+                        case TypeCode.UInt32:
+                            return Enum.ToObject(type, VariantUtils.ConvertToUInt32(variant));
+                        case TypeCode.UInt64:
+                            return Enum.ToObject(type, VariantUtils.ConvertToUInt64(variant));
+                        default:
+                        {
+                            GD.PushError(
+                                "Attempted to convert Variant to enum value of unsupported underlying type. Name: " +
+                                type.FullName + " : " + enumUnderlyingType.FullName + ".");
+                            return null;
+                        }
+                    }
+                }
+
+                if (type.IsGenericType)
+                {
+                    var genericTypeDef = type.GetGenericTypeDefinition();
+
+                    if (genericTypeDef == typeof(Godot.Collections.Dictionary<,>))
+                    {
+                        var ctor = type.GetConstructor(BindingFlags.Default,
+                            new[] { typeof(Godot.Collections.Dictionary) });
+
+                        if (ctor == null)
+                            throw new InvalidOperationException("Dictionary constructor not found");
+
+                        return ctor.Invoke(new object?[]
+                        {
+                            VariantUtils.ConvertTo<Godot.Collections.Dictionary>(variant)
+                        });
+                    }
+
+                    if (genericTypeDef == typeof(Godot.Collections.Array<>))
+                    {
+                        var ctor = type.GetConstructor(BindingFlags.Default,
+                            new[] { typeof(Godot.Collections.Array) });
+
+                        if (ctor == null)
+                            throw new InvalidOperationException("Array constructor not found");
+
+                        return ctor.Invoke(new object?[]
+                        {
+                            VariantUtils.ConvertTo<Godot.Collections.Array>(variant)
+                        });
+                    }
+                }
+
+                GD.PushError($"Attempted to convert Variant to unsupported type. Name: {type.FullName}.");
+                return null;
+            }
+        }
     }
 }
diff --git a/modules/mono/glue/GodotSharp/GodotSharp/Core/NativeInterop/Marshaling.cs b/modules/mono/glue/GodotSharp/GodotSharp/Core/NativeInterop/Marshaling.cs
index fd1d723c05..6176093bc1 100644
--- a/modules/mono/glue/GodotSharp/GodotSharp/Core/NativeInterop/Marshaling.cs
+++ b/modules/mono/glue/GodotSharp/GodotSharp/Core/NativeInterop/Marshaling.cs
@@ -1,5 +1,7 @@
 using System;
 using System.Runtime.InteropServices;
+using Godot.Collections;
+using Array = System.Array;
 
 // ReSharper disable InconsistentNaming
 
@@ -148,6 +150,15 @@ namespace Godot.NativeInterop
                     {
                         if (typeof(Godot.Object).IsAssignableFrom(type))
                             return Variant.Type.Object;
+
+                        // We use `IsAssignableFrom` with our helper interfaces to detect generic Godot collections
+                        // because `GetGenericTypeDefinition` is not supported in NativeAOT reflection-free mode.
+
+                        if (typeof(IGenericGodotDictionary).IsAssignableFrom(type))
+                            return Variant.Type.Dictionary;
+
+                        if (typeof(IGenericGodotArray).IsAssignableFrom(type))
+                            return Variant.Type.Array;
                     }
                     else if (type == typeof(Variant))
                     {
@@ -183,407 +194,6 @@ namespace Godot.NativeInterop
             return Variant.Type.Nil;
         }
 
-        /* TODO: Reflection and type checking each time is slow. This will be replaced with source generators. */
-        public static godot_variant ConvertManagedObjectToVariant(object? p_obj)
-        {
-            if (p_obj == null)
-                return new godot_variant();
-
-            switch (p_obj)
-            {
-                case bool @bool:
-                    return VariantUtils.CreateFromBool(@bool);
-                case char @char:
-                    return VariantUtils.CreateFromInt(@char);
-                case sbyte @int8:
-                    return VariantUtils.CreateFromInt(@int8);
-                case short @int16:
-                    return VariantUtils.CreateFromInt(@int16);
-                case int @int32:
-                    return VariantUtils.CreateFromInt(@int32);
-                case long @int64:
-                    return VariantUtils.CreateFromInt(@int64);
-                case byte @uint8:
-                    return VariantUtils.CreateFromInt(@uint8);
-                case ushort @uint16:
-                    return VariantUtils.CreateFromInt(@uint16);
-                case uint @uint32:
-                    return VariantUtils.CreateFromInt(@uint32);
-                case ulong @uint64:
-                    return VariantUtils.CreateFromInt(@uint64);
-                case float @float:
-                    return VariantUtils.CreateFromFloat(@float);
-                case double @double:
-                    return VariantUtils.CreateFromFloat(@double);
-                case Vector2 @vector2:
-                    return VariantUtils.CreateFromVector2(@vector2);
-                case Vector2i @vector2i:
-                    return VariantUtils.CreateFromVector2i(@vector2i);
-                case Rect2 @rect2:
-                    return VariantUtils.CreateFromRect2(@rect2);
-                case Rect2i @rect2i:
-                    return VariantUtils.CreateFromRect2i(@rect2i);
-                case Transform2D @transform2D:
-                    return VariantUtils.CreateFromTransform2D(@transform2D);
-                case Vector3 @vector3:
-                    return VariantUtils.CreateFromVector3(@vector3);
-                case Vector3i @vector3i:
-                    return VariantUtils.CreateFromVector3i(@vector3i);
-                case Vector4 @vector4:
-                    return VariantUtils.CreateFromVector4(@vector4);
-                case Vector4i @vector4i:
-                    return VariantUtils.CreateFromVector4i(@vector4i);
-                case Basis @basis:
-                    return VariantUtils.CreateFromBasis(@basis);
-                case Quaternion @quaternion:
-                    return VariantUtils.CreateFromQuaternion(@quaternion);
-                case Transform3D @transform3d:
-                    return VariantUtils.CreateFromTransform3D(@transform3d);
-                case Projection @projection:
-                    return VariantUtils.CreateFromProjection(@projection);
-                case AABB @aabb:
-                    return VariantUtils.CreateFromAABB(@aabb);
-                case Color @color:
-                    return VariantUtils.CreateFromColor(@color);
-                case Plane @plane:
-                    return VariantUtils.CreateFromPlane(@plane);
-                case Callable @callable:
-                    return VariantUtils.CreateFromCallable(@callable);
-                case SignalInfo @signalInfo:
-                    return VariantUtils.CreateFromSignalInfo(@signalInfo);
-                case Enum @enum:
-                    return VariantUtils.CreateFromInt(Convert.ToInt64(@enum));
-                case string @string:
-                    return VariantUtils.CreateFromString(@string);
-                case byte[] byteArray:
-                    return VariantUtils.CreateFromPackedByteArray(byteArray);
-                case int[] int32Array:
-                    return VariantUtils.CreateFromPackedInt32Array(int32Array);
-                case long[] int64Array:
-                    return VariantUtils.CreateFromPackedInt64Array(int64Array);
-                case float[] floatArray:
-                    return VariantUtils.CreateFromPackedFloat32Array(floatArray);
-                case double[] doubleArray:
-                    return VariantUtils.CreateFromPackedFloat64Array(doubleArray);
-                case string[] stringArray:
-                    return VariantUtils.CreateFromPackedStringArray(stringArray);
-                case Vector2[] vector2Array:
-                    return VariantUtils.CreateFromPackedVector2Array(vector2Array);
-                case Vector3[] vector3Array:
-                    return VariantUtils.CreateFromPackedVector3Array(vector3Array);
-                case Color[] colorArray:
-                    return VariantUtils.CreateFromPackedColorArray(colorArray);
-                case StringName[] stringNameArray:
-                    return VariantUtils.CreateFromSystemArrayOfStringName(stringNameArray);
-                case NodePath[] nodePathArray:
-                    return VariantUtils.CreateFromSystemArrayOfNodePath(nodePathArray);
-                case RID[] ridArray:
-                    return VariantUtils.CreateFromSystemArrayOfRID(ridArray);
-                case Godot.Object[] godotObjectArray:
-                    return VariantUtils.CreateFromSystemArrayOfGodotObject(godotObjectArray);
-                case Godot.Object godotObject:
-                    return VariantUtils.CreateFromGodotObject(godotObject);
-                case StringName stringName:
-                    return VariantUtils.CreateFromStringName(stringName);
-                case NodePath nodePath:
-                    return VariantUtils.CreateFromNodePath(nodePath);
-                case RID rid:
-                    return VariantUtils.CreateFromRID(rid);
-                case Collections.Dictionary godotDictionary:
-                    return VariantUtils.CreateFromDictionary(godotDictionary);
-                case Collections.Array godotArray:
-                    return VariantUtils.CreateFromArray(godotArray);
-                case Collections.IGenericGodotDictionary godotDictionary:
-                    return VariantUtils.CreateFromDictionary(godotDictionary.UnderlyingDictionary);
-                case Collections.IGenericGodotArray godotArray:
-                    return VariantUtils.CreateFromArray(godotArray.UnderlyingArray);
-                case Variant variant:
-                    return NativeFuncs.godotsharp_variant_new_copy((godot_variant)variant.NativeVar);
-            }
-
-            GD.PushError("Attempted to convert an unmarshallable managed type to Variant. Name: '" +
-                         p_obj.GetType().FullName + ".");
-            return new godot_variant();
-        }
-
-        public static object? ConvertVariantToManagedObjectOfType(in godot_variant p_var, Type type)
-        {
-            // This function is only needed to set the value of properties. Fields have their own implementation, set_value_from_variant.
-            switch (Type.GetTypeCode(type))
-            {
-                case TypeCode.Boolean:
-                    return VariantUtils.ConvertToBool(p_var);
-                case TypeCode.Char:
-                    return VariantUtils.ConvertToChar(p_var);
-                case TypeCode.SByte:
-                    return VariantUtils.ConvertToInt8(p_var);
-                case TypeCode.Int16:
-                    return VariantUtils.ConvertToInt16(p_var);
-                case TypeCode.Int32:
-                    return VariantUtils.ConvertToInt32(p_var);
-                case TypeCode.Int64:
-                    return VariantUtils.ConvertToInt64(p_var);
-                case TypeCode.Byte:
-                    return VariantUtils.ConvertToUInt8(p_var);
-                case TypeCode.UInt16:
-                    return VariantUtils.ConvertToUInt16(p_var);
-                case TypeCode.UInt32:
-                    return VariantUtils.ConvertToUInt32(p_var);
-                case TypeCode.UInt64:
-                    return VariantUtils.ConvertToUInt64(p_var);
-                case TypeCode.Single:
-                    return VariantUtils.ConvertToFloat32(p_var);
-                case TypeCode.Double:
-                    return VariantUtils.ConvertToFloat64(p_var);
-                case TypeCode.String:
-                    return VariantUtils.ConvertToStringObject(p_var);
-                default:
-                {
-                    if (type == typeof(Vector2))
-                        return VariantUtils.ConvertToVector2(p_var);
-
-                    if (type == typeof(Vector2i))
-                        return VariantUtils.ConvertToVector2i(p_var);
-
-                    if (type == typeof(Rect2))
-                        return VariantUtils.ConvertToRect2(p_var);
-
-                    if (type == typeof(Rect2i))
-                        return VariantUtils.ConvertToRect2i(p_var);
-
-                    if (type == typeof(Transform2D))
-                        return VariantUtils.ConvertToTransform2D(p_var);
-
-                    if (type == typeof(Vector3))
-                        return VariantUtils.ConvertToVector3(p_var);
-
-                    if (type == typeof(Vector3i))
-                        return VariantUtils.ConvertToVector3i(p_var);
-
-                    if (type == typeof(Vector4))
-                        return VariantUtils.ConvertToVector4(p_var);
-
-                    if (type == typeof(Vector4i))
-                        return VariantUtils.ConvertToVector4i(p_var);
-
-                    if (type == typeof(Basis))
-                        return VariantUtils.ConvertToBasis(p_var);
-
-                    if (type == typeof(Quaternion))
-                        return VariantUtils.ConvertToQuaternion(p_var);
-
-                    if (type == typeof(Transform3D))
-                        return VariantUtils.ConvertToTransform3D(p_var);
-
-                    if (type == typeof(Projection))
-                        return VariantUtils.ConvertToProjection(p_var);
-
-                    if (type == typeof(AABB))
-                        return VariantUtils.ConvertToAABB(p_var);
-
-                    if (type == typeof(Color))
-                        return VariantUtils.ConvertToColor(p_var);
-
-                    if (type == typeof(Plane))
-                        return VariantUtils.ConvertToPlane(p_var);
-
-                    if (type == typeof(Callable))
-                        return VariantUtils.ConvertToCallableManaged(p_var);
-
-                    if (type == typeof(SignalInfo))
-                        return VariantUtils.ConvertToSignalInfo(p_var);
-
-                    if (type.IsEnum)
-                    {
-                        var enumUnderlyingType = type.GetEnumUnderlyingType();
-                        switch (Type.GetTypeCode(enumUnderlyingType))
-                        {
-                            case TypeCode.SByte:
-                                return VariantUtils.ConvertToInt8(p_var);
-                            case TypeCode.Int16:
-                                return VariantUtils.ConvertToInt16(p_var);
-                            case TypeCode.Int32:
-                                return VariantUtils.ConvertToInt32(p_var);
-                            case TypeCode.Int64:
-                                return VariantUtils.ConvertToInt64(p_var);
-                            case TypeCode.Byte:
-                                return VariantUtils.ConvertToUInt8(p_var);
-                            case TypeCode.UInt16:
-                                return VariantUtils.ConvertToUInt16(p_var);
-                            case TypeCode.UInt32:
-                                return VariantUtils.ConvertToUInt32(p_var);
-                            case TypeCode.UInt64:
-                                return VariantUtils.ConvertToUInt64(p_var);
-                            default:
-                            {
-                                GD.PushError(
-                                    "Attempted to convert Variant to enum value of unsupported underlying type. Name: " +
-                                    type.FullName + " : " + enumUnderlyingType.FullName + ".");
-                                return null;
-                            }
-                        }
-                    }
-
-                    if (type.IsArray || type.IsSZArray)
-                    {
-                        return ConvertVariantToSystemArrayOfType(p_var, type);
-                    }
-                    else if (type.IsGenericType)
-                    {
-                        if (typeof(Godot.Object).IsAssignableFrom(type))
-                        {
-                            var godotObject = VariantUtils.ConvertToGodotObject(p_var);
-
-                            if (!type.IsInstanceOfType(godotObject))
-                            {
-                                GD.PushError("Invalid cast when marshaling Godot.Object type." +
-                                             $" `{godotObject.GetType()}` is not assignable to `{type.FullName}`.");
-                                return null;
-                            }
-
-                            return godotObject;
-                        }
-
-                        return null;
-                    }
-                    else if (type == typeof(Variant))
-                    {
-                        return Variant.CreateCopyingBorrowed(p_var);
-                    }
-
-                    if (ConvertVariantToManagedObjectOfClass(p_var, type, out object? res))
-                        return res;
-
-                    break;
-                }
-            }
-
-            GD.PushError("Attempted to convert Variant to unsupported type. Name: " +
-                         type.FullName + ".");
-            return null;
-        }
-
-        private static object? ConvertVariantToSystemArrayOfType(in godot_variant p_var, Type type)
-        {
-            if (type == typeof(byte[]))
-                return VariantUtils.ConvertAsPackedByteArrayToSystemArray(p_var);
-
-            if (type == typeof(int[]))
-                return VariantUtils.ConvertAsPackedInt32ArrayToSystemArray(p_var);
-
-            if (type == typeof(long[]))
-                return VariantUtils.ConvertAsPackedInt64ArrayToSystemArray(p_var);
-
-            if (type == typeof(float[]))
-                return VariantUtils.ConvertAsPackedFloat32ArrayToSystemArray(p_var);
-
-            if (type == typeof(double[]))
-                return VariantUtils.ConvertAsPackedFloat64ArrayToSystemArray(p_var);
-
-            if (type == typeof(string[]))
-                return VariantUtils.ConvertAsPackedStringArrayToSystemArray(p_var);
-
-            if (type == typeof(Vector2[]))
-                return VariantUtils.ConvertAsPackedVector2ArrayToSystemArray(p_var);
-
-            if (type == typeof(Vector3[]))
-                return VariantUtils.ConvertAsPackedVector3ArrayToSystemArray(p_var);
-
-            if (type == typeof(Color[]))
-                return VariantUtils.ConvertAsPackedColorArrayToSystemArray(p_var);
-
-            if (type == typeof(StringName[]))
-                return VariantUtils.ConvertToSystemArrayOfStringName(p_var);
-
-            if (type == typeof(NodePath[]))
-                return VariantUtils.ConvertToSystemArrayOfNodePath(p_var);
-
-            if (type == typeof(RID[]))
-                return VariantUtils.ConvertToSystemArrayOfRID(p_var);
-
-            if (typeof(Godot.Object[]).IsAssignableFrom(type))
-                return VariantUtils.ConvertToSystemArrayOfGodotObject(p_var, type);
-
-            GD.PushError("Attempted to convert Variant to array of unsupported element type. Name: " +
-                         type.GetElementType()!.FullName + ".");
-            return null;
-        }
-
-        private static bool ConvertVariantToManagedObjectOfClass(in godot_variant p_var, Type type,
-            out object? res)
-        {
-            if (typeof(Godot.Object).IsAssignableFrom(type))
-            {
-                if (p_var.Type == Variant.Type.Nil)
-                {
-                    res = null;
-                    return true;
-                }
-
-                if (p_var.Type != Variant.Type.Object)
-                {
-                    GD.PushError("Invalid cast when marshaling Godot.Object type." +
-                                 $" Variant type is `{p_var.Type}`; expected `{p_var.Object}`.");
-                    res = null;
-                    return true;
-                }
-
-                var godotObjectPtr = VariantUtils.ConvertToGodotObjectPtr(p_var);
-
-                if (godotObjectPtr == IntPtr.Zero)
-                {
-                    res = null;
-                    return true;
-                }
-
-                var godotObject = InteropUtils.UnmanagedGetManaged(godotObjectPtr);
-
-                if (!type.IsInstanceOfType(godotObject))
-                {
-                    GD.PushError("Invalid cast when marshaling Godot.Object type." +
-                                 $" `{godotObject.GetType()}` is not assignable to `{type.FullName}`.");
-                    res = null;
-                    return false;
-                }
-
-                res = godotObject;
-                return true;
-            }
-
-            if (typeof(StringName) == type)
-            {
-                res = VariantUtils.ConvertToStringNameObject(p_var);
-                return true;
-            }
-
-            if (typeof(NodePath) == type)
-            {
-                res = VariantUtils.ConvertToNodePathObject(p_var);
-                return true;
-            }
-
-            if (typeof(RID) == type)
-            {
-                res = VariantUtils.ConvertToRID(p_var);
-                return true;
-            }
-
-            if (typeof(Collections.Dictionary) == type)
-            {
-                res = VariantUtils.ConvertToDictionaryObject(p_var);
-                return true;
-            }
-
-            if (typeof(Collections.Array) == type)
-            {
-                res = VariantUtils.ConvertToArrayObject(p_var);
-                return true;
-            }
-
-            res = null;
-            return false;
-        }
-
         // String
 
         public static unsafe godot_string ConvertStringToNative(string? p_mono_string)
diff --git a/modules/mono/glue/GodotSharp/GodotSharp/Core/NativeInterop/VariantUtils.generic.cs b/modules/mono/glue/GodotSharp/GodotSharp/Core/NativeInterop/VariantUtils.generic.cs
index 694da6db77..80ef2a1ea1 100644
--- a/modules/mono/glue/GodotSharp/GodotSharp/Core/NativeInterop/VariantUtils.generic.cs
+++ b/modules/mono/glue/GodotSharp/GodotSharp/Core/NativeInterop/VariantUtils.generic.cs
@@ -4,6 +4,8 @@ using System.Runtime.CompilerServices;
 
 namespace Godot.NativeInterop;
 
+#nullable enable
+
 public partial class VariantUtils
 {
     private static Exception UnsupportedType<T>() => new InvalidOperationException(