Unable to load Array of custom classes directly from load/preload to statically typed variable

[Zain-A-Abbas]

Tested versions

• Reproducible in v4.3.stable.official [77dcf97]
• Not present in v4.2.stable.official [46dc277]

System information

Godot v4.3.stable - Windows 10.0.19045 - Vulkan (Forward+) - dedicated NVIDIA GeForce RTX 3060 (NVIDIA; 31.0.15.3742) - AMD Ryzen 5 3600 6-Core Processor (12 Threads)

Issue description

In 4.2 and earlier, one could load arrays of custom object types directly from a loaded resource file in one line. E.g. var myvar: Array[SomeResource] = preload("somefile.tres").someVariable. Now, it gives the following error message: "Cannot assign a value of type Array[res://SomeResource.gd] to variable "myvar" with specified type Array[SomeResource]."

No error is brought up and code runs as usual if myvar is not statically typed. The error is also avoided if split up into two lines, e.g.

var myvar = preload("somefile.tres")
var yourvar: Array[SomeResource] = myvar.someVariable

Steps to reproduce

In the minimum reproduction project, the node.gd file will display the error. It can be reproduced by

1. Creating a custom class
2. Creating a resource with an array of that class as a variable
3. Trying to load that data into a statically typed variable.

Minimal reproduction project (MRP)

Bug-Reporting.zip

Bugsquad edit: Fix formatting.

[goblinrockcandy]

I also encountered this problem. However, note that for me, it worked using load() would work, but preload() would not.

This is my reproduction:

# custom_resource.gd:
class_name CustomResource
extends Resource

# custom_resource_list.gd
class_name CustomResourceList
extends Resource

@export var array: Array[CustomResource]

# main.gd
extends Node

const SAVED_CUSTOM_RESOURCE_LIST = preload("res://saved_custom_resource_list.tres")

# This works!
func _loaded_array_resource() -> void:
	var loaded: CustomResourceList = load("res://saved_custom_resource_list.tres")
	for custom_resource: CustomResource in loaded.array:
		print(custom_resource)


# This does not work.
func _preloaded_array_resource() -> void:
	for custom_resource: CustomResource in SAVED_CUSTOM_RESOURCE_LIST.array:  # error here!
		print(custom_resource)

This is the error message:
Unable to iterate on value of type "Array[res://custom_resource.gd]" with variable of type "CustomResource".

[smedelyan]

EDIT

Sorry, I haven't read the issue to the end. My reply is irrelevant

---

ORIGINAL REPLY

In 4.2.2 there were issues with typed arrays, e.g. you couldn't do things like this:

var typed_arr: Array[String] = []
var plain_arr: Array = ["test"]
typed_arr = plain_arr # this will fail
typed_arr.assign(plain_arr) # this will be ok

I think the issue is that the const / vars above are not typed and maybe treated as Variant-s. If this is the case, then it is valid because the types of entities don't match.

I recall that I had issues with definined typed consts when used with preload() in 4.2.2 (e.g. const MY_CONST: MyType = preload("...") didn't work even if casted as preload("...") as MyType). But maybe now it's working?

Can you try to use := assignment or specify the type explicitly?

[matheusmdx]

Bisecting points to #92544 as the culprit: