Document @GDScript.is_instance_of method

[dalexeev]

This function was added in #73489.

CC @vonagam

[akien-mga]

Given the recent bug reports we got, it seems like users use it this way:

var a = 5
var b = 42
print(is_instance_of(a, b))

Provided this does work, I don't think it's covered by the list below.

[dalexeev]

It doesn't work because 42 >= Variant::VARIANT_MAX.

godot/modules/gdscript/gdscript_utility_functions.cpp

Lines 530 to 541 in 5f3dee5

	if (p_args[1]->get_type() == Variant::INT) {
	int builtin_type = *p_args[1];
	if (builtin_type < 0 || builtin_type >= Variant::VARIANT_MAX) {
	*r_ret = RTR("Invalid type argument for is_instance_of(), use TYPE_* constants for built-in types.");
	r_error.error = Callable::CallError::CALL_ERROR_INVALID_ARGUMENT;
	r_error.argument = 1;
	r_error.expected = Variant::NIL;
	return;
	}
	*r_ret = p_args[0]->get_type() == builtin_type;
	return;
	}

[akien-mga]

I was thinking of #73663, but I guess this was just a bogus example? I thought they were trying to use this to confirm that both variants are ints.

[dalexeev]

In the issue, I first thought the user was trying to use is like in Python. But maybe it really was just a bad example and the problem was the confusing error message.

[akien-mga]

Thanks!

[dalexeev]

I shouldn't have written about performance, especially without tests. This is too implementation dependent. But I'm surprised that is_instance_of() is faster, if my tests are correct.