GDScript function parameters statically typed as script-defined classes can't be given a default value

[MidZik]

Godot version: 3.1 beta 10

Issue description:

class A extends Reference:
	var a

func do_thing(parameter : A = null): # causes error
	pass

func do_different_thing(parameter : A = A.new()): # also causes error
	pass

The above script causes an error on line 4 (the function definition): Value type (null) doesn't match the type of argument 'parameter' (parameter).

Line 7 causes a similar error.

If parameter is statically typed as any built-in class instead, it works fine. It's only for script-defined classes that the error appears.

[ghost]

Would be nice to allow for this in situations where you follow with if(parameter) to see if one was provided, but I think that it probably has to be a variant to include null.

@vnen Currently, is there a proper way of typing an argument to a specific class, and making it optional at the same time?

[MidZik]

I don't know why I specified Reference specifically, this happens with all custom classes.

GDScript allows you to assign null to variables statically typed as custom classes, so it should do the same for function parameters.

[MidZik]

I tested a bit more and realized you can't set any default value, it's not limited to just null.

Updating the issue now.

[xDGameStudios]

I tested a bit more and realized you can't set any default value, it's not limited to just null.

Updating the issue now.

Can also confirm this:

func do_different_thing(parameter : A = A.new()): # also causes error
	pass

[jabcross]

Seconding this. As we don't have mandatory typing, and we'll probably never have the need for Option or something like it, I feel that this is feature is a must.

[Zylann]

Still happens in Godot 3.2 beta2