InvalidCastException is thrown when trying to assign a c# resource to a tool Node in editor

[Saplonily]

Godot version

v4.2 dev.mono 16a9356

System information

Godot v4.2.dev.mono (16a9356) - Windows 10.0.19045 - Vulkan (Forward+) - integrated Intel(R) UHD Graphics 630 (Intel Corporation; 31.0.101.2121) - Intel(R) Core(TM) i5-10400 CPU @ 2.90GHz (12 Threads)

Issue description

InvalidCastException thrown when trying to assign a c# resource to a tool Node in editor.
Actually this bug has been here since c# Resource is supported.

The exception stack:

D:/godot/modules/mono/glue/GodotSharp/GodotSharp/Core/NativeInterop/ExceptionUtils.cs:112 - System.InvalidCastException: Unable to cast object of type 'Godot.Resource' to type 'CSharpResource'.
     at CSharpNode.SetGodotClassPropertyValue(godot_string_name& name, godot_variant& value) in D:\csres\Godot.SourceGenerators\Godot.SourceGenerators.ScriptPropertiesGenerator\CSharpNode_ScriptProperties.generated.cs:line 13
     at Godot.Bridge.CSharpInstanceBridge.Set(IntPtr godotObjectGCHandle, godot_string_name* name, godot_variant* value) in D:\godot\modules\mono\glue\GodotSharp\GodotSharp\Core\Bridge\CSharpInstanceBridge.cs:line 57

Steps to reproduce

1. Make a new scene with a single Node Node
2. Declare a new c# resource class:

using Godot;
[GlobalClass]
public partial class CSharpResource : Resource
{
    // some props...
    [Export] public int AInt { get; set; }
}

3. Attach a c# script named CSharpNode.cs with a CSharpResource property and tool enabled(necessary) to the Node:

using Godot;
[GlobalClass, Tool]
public partial class CSharpNode : Node
{
    [Export] CSharpResource MyRes { get; set; }
}

4. Reopen the scene to make Tool works.
5. Assign a CSharpResource to the MyRes property.
6. Then the exception is thrown.

Minimal reproduction project

csres.zip

[raulsntos]

You forgot to add the [Tool] attribute to CSharpResource. Every script referenced in a Tool script needs to also be a Tool script so it can be instantiated in the editor.

• Duplicate of In C#, resources not being loaded in Tool scripts #55596.

[Saplonily]

You forgot to add the [Tool] attribute to CSharpResource. Every script referenced in a Tool script needs to also be a Tool script so it can be instantiated in the editor.

• Duplicate of In C#, resources not being loaded in Tool scripts #55596.

Thanks for replying! It works.
Maybe we can print a friendlier error about the need to add the Tool attribute instead of instantiating a Resource that leads to InvalidCastException?