GDScript 2.0: Can't use not operator (!) with String, Dictionary, or Array unless const

[Error7Studios]

Godot version

4.0 alpha 3

System information

Windows 10

Issue description

In Godot 4, empty String, Array, and Dictionary values convert to true booleans, unlike Godot 3.
Is this intended?

Also, you can no longer use not/! in front of said values, unless they're saved into a const.

Steps to reproduce

extends Node

const VALUE = {}

func _ready():
	var val = VALUE				# Error
#	var val := VALUE			# Error (static type)
#	const val = VALUE			# OK
#	const val := VALUE			# OK (static type)
	
	if !val:
		print(val, " is falsy")
	else:
		print(val, " is truthy")

Minimal reproduction project

Godot4 NOT Operator.zip

[dalexeev]

#	const val = VALUE			# OK
#	const val := VALUE			# OK (static type)

In RC 1, all 4 options give the same error (Invalid operand of type "Dictionary" for unary operator "not".).

[YuriSizov]

Also all 3 types have a method to explicitly test for emptiness that should be used. I wouldn't call this a regression, it's more of a change for consistency.

[decree]

So this is intended behaviour and not a bug?

As i'm porting my old Godot 3.5 project to Godot 4, i have tons of if not <string> or if not <dictionary> checks which now result to an error. I think the old 3.5 way to do a simple if not x was an effective and clean way to check things, because it worked with any variable without or with typing.

[FilipLundby]

If this is about consistency, I'm curious why it's allow to test on strings as long as you do not use ! and not. For instance in C# if ("hello world") ... is not allowed, while in JavaScript you can do both if ("hello world") ... and if (!"hello world") ....

# Prints "A"
if "Go-dot, or go home":
	print("A")
else:
	print("B")

# Prints "B"
if "":
	print("A")
else:
	print("B")

# Invalid operand of type "String" for unary operator "not".
if !"": 
	print("A")
else:
	print("B")

To me this seems inconsistent.

Godot 4.0 RC 5

[Lippanon]

I also agree it seems inconsistent to allow:

var example_dict :Dictionary = {}
if example_dict:
	pass

But not allow not example_dict. I use the example above to check the result of intersect_ray frequently and finding out I can't check its negation like that made me question if the example above can result in undefined behavior.