Add safe comparison operator (===)

[dalexeev]

Godot version:
3.1.1.stable.official

Issue description:
At this point, the == operator can only compare values of the same type:

var x = 2
print(x == true) # Error: Invalid operands 'int' and 'bool' in operator '=='

This is absolutely the right decision, but sometimes it can be inconvenient. For example, if a function returns a value of an arbitrary type, you have to check both the type and the value.

var res = my_func()
if res is String and res == "":
    do_something()

I propose to add the operator ===, which allows you to compare the value of any type with the value of any type. Herewith:

1. If A and B are values of different types, then A === B is always false.
2. If A and B are of the same type, then A === B is always equal to A == B.

Then the condition in the example will be a little easier:

var res = my_func()
if res === "":
    do_something()

P. S. And still need the opposite operator, of course.
P. P. S. You can think about the syntax of the operator.

UPD. my_func() can return a value of any type (e.g. a string or a boolean). And in this case, I need to check that the function returned false, not "" or 0, for example.
UPD 2. Although now I think it's better to change the behavior of the == operator. (#26375)

[dalexeev]

var x = 2
print(x == "2") # Error: Invalid operands 'int' and 'String' in operator '=='

In Python:

>>> 2 == '2'
False

However, no errors.

[KoBeWi]

Related: #26375

[aaronfranke]

var res = my_func()
if res is bool and res == false:
    do_something()

Alternatively:

var res: bool = my_func()
if !res:
    do_something()

You should not be using == false or == true because it is bad practice and produces confusing logical statements that could otherwise be much simpler.

[dalexeev]

1. This does not always work as expected:

var x = "abc"
var res: bool = x
print(res) # prints 'abc'
print(res == true) # Error: Invalid operands 'String' and 'bool' in operator '=='

var x = null
var res: String = x
print(res) # prints 'Null'
print(res.length()) # Error: Invalid call. Nonexistent function 'length' in base 'Nil'

2. my_func() can return a value of any type (e.g. a string or a boolean). And in this case, I need to check that the function returned false, not "" or 0, for example.

[aaronfranke]

@dalexeev That's really weird, I can confirm this behavior, but that's definitely a bug. @vnen You should check this out, it seems that typed GDScript is not working at all here.

[dalexeev]

static func eq(a, b) -> bool: # a === b # a ?= b # a =?= b
    return typeof(a) == typeof(b) and a == b

[zkmark]

It's 2023, couldn't they add that very important functionality in godot 4?

[dalexeev]

• See also Add strict and safe equality operator === for comparing references and variants (implemented as is_same() method) godot-proposals#6092.

There is is_same() global function.