Lambdas lose context when used with signals and call_deferred()

[HotNoggin]

Tested versions

• Reproducible in 4.2.2 Stable

System information

Godot v4.2.2.stable - Windows 10.0.22631 - Vulkan (Forward+) - dedicated NVIDIA GeForce RTX 3050 Ti Laptop GPU (NVIDIA; 31.0.15.5222) - AMD Ryzen 9 6900HS with Radeon Graphics (16 Threads)

Issue description

When working on my snake project, I had used this lambda in _ready():

func _ready() -> void:
    hurtbox.area_entered.connect(func(area: Area2D) -> void:
	    if area is Collectable:
		    var collectable: Collectable = area as Collectable
		    #CRITICAL This doesn't work without "self". Engine bug?
		    self.add_segment.call_deferred(false)
		    collectable.collect()
    )

When the self in self.add_segment.call_deferred(false) is removed, there is an error, which appears to say that the object calling this method doesn't exist! What the function does isn't too relevant, because a friend reproduced the error with minimal effort (as seen below in the steps to reproduce).

Steps to reproduce

Simply use this code in your project:

signal test

func _ready() -> void:
    test.connect(func(): do_thing.call_deferred())

func do_thing() -> void:
    print("hello")

func _process(delta: float) -> void:
    if Input.is_action_just_pressed("ui_accept"):
        test.emit()

You'll be met with this error when you press the key:

You'll also notice in the debugger that all of the object's properties are missing (this might not be a part of the bug, though), and only the properties from the lambda are shown.
Adding self before do_thing will also cause the issue to vanish.

Minimal reproduction project (MRP)

Lambda Reproduction Project.zip

[vnen]

I can reproduce on 4.2.2 but not on master. I assume this has already been fixed.

[dalexeev]

I can reproduce on 4.2.2 but not on master. I assume this has already been fixed.

• Probably it was fixed by GDScript: Fix access non-static members in static context #91412 (comment).