I got this error in this function: Invalid operands 'float' and 'Vector2' in operator '!=' - godot

Question

func move(motion):
if motion != Vector2():
target_angle = atan2(motion.x, motion.y) - PI/2
Skin.set_rot(target_angle)
I tried converting vectors to ints. I looked up this error and didnt understand fixes.

Answer 1

What does motion != Vector2() mean?
It is comparing two things to see if the are different:
motion a variable parameter of the function move which is Variant (it does not have a declared type).
Vector2() this is the default constructor of the Vector2 type. It should be equivalent to Vector2.ZERO or Vector2(0.0, 0.0).
Now, the error is telling you that you got a float, and that Godot does not know how to compare float and Vector2.
You might have expected that checking if a float is different from a Vector2 would return true (a float is different from a Vector2), but no, the comparison is an error. Yes, I tried. Otherwise the execution flow would enter the conditional and try to execute atan2(motion.x, motion.y) with a float and that would be error.
This means you need to ensure it is a Vector2 before comparing it with another Vector2.
You could have prevented getting a float here by declaring the type of the parameter:
func move(motion:Vector2):
if motion != Vector2():
target_angle = atan2(motion.x, motion.y) - PI/2
Skin.set_rot(target_angle)
And now it would give you an error where you are calling it with a float. Why or where are you calling it with a float? I don't know. Presumably if you are getting the error in runtime you can also find out by looking at the stack on the debugger panel when the error shows up. Otherwise, this is a sure way to find out.
By the way, aren't the parameters of atan2 backwards? Are you aware of motion.angle()?
Anyway, Bugfish is right that you can check if the type of motion is Vector2 in runtime, for example: typeof(motion) == TYPE_VECTOR2.
If I understand correctly you claim you did this: var motion = Vector2(). Well, something else happened somewhere, and we cannot find it for you. I presume you change the value of motion somewhere (that is the point of having a variable) perhaps set it to the return value of a function var motion = get_motion() or similar, and it sometimes returns a float...
Which, reminds me, you can also specify what your methods return. This method returns nothing (void):
func move(motion:Vector2) -> void:
if motion != Vector2():
target_angle = atan2(motion.x, motion.y) - PI/2
Skin.set_rot(target_angle)
And this one returns a Vector2:
func get_motion() -> Vector2:
return Input.get_vector("ui_left", "ui_right", "ui_up", "ui_down")
Yes, GDScript has static types, use them!

Answer 2

Well it seems like your parameter motion does not contain a Vector2, but a float value. Where do you call the function and did you already check if the functions gets the parameter you wanted to pass it?
Also before using a vatiable with unknown type, You should check the type, before assuming it's an Vector.
One way would be to check it's type:
if typeof(motion) != TYPE_VECTOR2:
return