Ternary with sibling classes warns of incompatible types

[ashtonmeuser]

Godot version

3.4.4

System information

macOS 10.15.7

Issue description

Sibling classes extending the same base class report incompatible types when assigning using a ternary. A warning is produced stating the following.

Values of the ternary conditional are not mutually compatible

The same does not occur for a ternary producing type of superclass or subclass as follows.

var _dummy: DummySuper = DummySuper.new() if true else DummySub0.new()

Steps to reproduce

1. Create a superclass.

   extends Node
   class_name DummySuper

2. Create two subclasses that each extend the superclass.

   extends DummySuper
   class_name DummySub0

   extends DummySuper
   class_name DummySub1

3. Instatiate a variable of type superclass as one or the other subclass in a ternary.

   var _dummy: DummySuper = DummySub0.new() if true else DummySub1.new()

Minimal reproduction project

ternary_repro.zip

[salamandars]

At first glance it looks like the type compatibility check in the gdscript parser only checks for parent-child relationships, not siblings?

You can avoid the warning by casting to the super class: var _dummy: DummySuper = DummySub0.new() as DummySuper if true else DummySub1.new() as DummySuper

[PrinceMerluza]

Still happens on Godot 4b12. The workaround works for now.