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.

2 files changed, 16 insertions, 14 deletions

diff --git a/modules/mono/editor/GodotTools/GodotTools/GodotSharpEditor.cs b/modules/mono/editor/GodotTools/GodotTools/GodotSharpEditor.cs
index 89364d1c02..54969920cb 100644
--- a/modules/mono/editor/GodotTools/GodotTools/GodotSharpEditor.cs
+++ b/modules/mono/editor/GodotTools/GodotTools/GodotSharpEditor.cs
@@ -455,7 +455,7 @@ namespace GodotTools
             _menuPopup.IdPressed += _MenuOptionPressed;
 
             // External editor settings
-            EditorDef("mono/editor/external_editor", ExternalEditorId.None);
+            EditorDef("mono/editor/external_editor", Variant.From(ExternalEditorId.None));
 
             string settingsHintStr = "Disabled";
 
diff --git a/modules/mono/editor/GodotTools/GodotTools/Internals/Globals.cs b/modules/mono/editor/GodotTools/GodotTools/Internals/Globals.cs
index acb7cc3ab0..45ae7eb86b 100644
--- a/modules/mono/editor/GodotTools/GodotTools/Internals/Globals.cs
+++ b/modules/mono/editor/GodotTools/GodotTools/Internals/Globals.cs
@@ -1,3 +1,4 @@
+using Godot;
 using Godot.NativeInterop;
 using System.Diagnostics.CodeAnalysis;
 using System.Runtime.CompilerServices;
@@ -8,30 +9,31 @@ namespace GodotTools.Internals
     {
         public static float EditorScale => Internal.godot_icall_Globals_EditorScale();
 
-        public static unsafe object GlobalDef(string setting, object defaultValue, bool restartIfChanged = false)
+        // ReSharper disable once UnusedMethodReturnValue.Global
+        public static Variant GlobalDef(string setting, Variant defaultValue, bool restartIfChanged = false)
         {
             using godot_string settingIn = Marshaling.ConvertStringToNative(setting);
-            using godot_variant defaultValueIn = Marshaling.ConvertManagedObjectToVariant(defaultValue);
-            Internal.godot_icall_Globals_GlobalDef(settingIn, defaultValueIn, restartIfChanged, out godot_variant result);
-            using (result)
-                return Marshaling.ConvertVariantToManagedObject(result);
+            using godot_variant defaultValueIn = defaultValue.CopyNativeVariant();
+            Internal.godot_icall_Globals_GlobalDef(settingIn, defaultValueIn, restartIfChanged,
+                out godot_variant result);
+            return Variant.CreateTakingOwnershipOfDisposableValue(result);
         }
 
-        public static unsafe object EditorDef(string setting, object defaultValue, bool restartIfChanged = false)
+        // ReSharper disable once UnusedMethodReturnValue.Global
+        public static Variant EditorDef(string setting, Variant defaultValue, bool restartIfChanged = false)
         {
             using godot_string settingIn = Marshaling.ConvertStringToNative(setting);
-            using godot_variant defaultValueIn = Marshaling.ConvertManagedObjectToVariant(defaultValue);
-            Internal.godot_icall_Globals_EditorDef(settingIn, defaultValueIn, restartIfChanged, out godot_variant result);
-            using (result)
-                return Marshaling.ConvertVariantToManagedObject(result);
+            using godot_variant defaultValueIn = defaultValue.CopyNativeVariant();
+            Internal.godot_icall_Globals_EditorDef(settingIn, defaultValueIn, restartIfChanged,
+                out godot_variant result);
+            return Variant.CreateTakingOwnershipOfDisposableValue(result);
         }
 
-        public static object EditorShortcut(string setting)
+        public static Variant EditorShortcut(string setting)
         {
             using godot_string settingIn = Marshaling.ConvertStringToNative(setting);
             Internal.godot_icall_Globals_EditorShortcut(settingIn, out godot_variant result);
-            using (result)
-                return Marshaling.ConvertVariantToManagedObject(result);
+            return Variant.CreateTakingOwnershipOfDisposableValue(result);
         }
 
         [SuppressMessage("ReSharper", "InconsistentNaming")]