Polymorphism doesn't work on a typed arrays

[GitHubPiotr]

Tested versions

Tested on Godot 4.3beta1

System information

Windows 10, Forward+

Issue description

I noticed that polymorphism doesn't work on arrays of a specific type. Example below

Steps to reproduce

1. Create new scene and attach a script
2. In the script create two new empty classes. Extend the second class by the first class
   
3. In _ready() function create variable of Array[Class that extends another class]
   
4. Create another variable of Array[Your primary class] and assign it with variable from step 3
   
5. Done. You getting a compiler error
   

Minimal reproduction project (MRP)

test.zip

[AThousandShips]

This is a current limitation, please see:

• Behavior of typed arrays godot-proposals#7364

[dalexeev]

Duplicate of:

• Functions accept typed arrays and cannot inherit conversions #80586
• Typed array function arguments don't accept typed arrays of subclass #83876
• TypedArray does not work with Inheritence #89959
• static type arrya cannot understand extends(subclass) #93063

See:

• GDScript reference - Typed arrays
• Behavior of typed arrays godot-proposals#7364

This is not a bug. Arrays are passed by reference; they do not copy the entire content. Otherwise you would get:

var a: Array[Node2D]
var b: Array[Node]
b = a # Now `b` refers to the same array as `a`.
b.append(Label.new()) # Valid, `Label` is a subtype of `Node`.
print(a[0]) # Invalid, `Label` is **not** a subtype of `Node2D`.

Probably the only way this would work is if the GDScript supported read/write qualifiers. But it's too difficult.

Thanks for the contribution nonetheless!