C# classes break allocation-free parity

[sakars]

Hi!
I would say I'm pretty new to the Godot engine, but as someone interested in memory management and language interop, I noticed something I really dislike. As far as I can see, calling the constructor new GodotObject() allocates a C++ Object implicitly. Said Object is not freed when GodotObject gets garbage collected. This breaks both allocation-free parity, and C# convention. This applies to all objects which inherit from Object/GodotObject.

This would entail major wide-reaching breaking changes in how C# bindings are used, but the changes themselves are relatively simple and they would solve this issue:

1. Create a GodotObject.New() static factory method. It behaves identically to how new GodotObject() behaves currently. This looks closer to how GDScript instantiation looks and restores allocation-free parity with Free().
2. new GodotObject() is either deleted, made protected, or if that is impossible due to inheritance issues, instantiates a GodotObject in a similar state to how instances behave after Dispose() is called on them. These instances would be effectively useless and throw on nearly all actions.

Because of the fact that a C++ object is never directly tied to the C# garbage collector, we (and thus the documentation) should not treat the C# classes as drop-in replacements to Objects. What they are, are adapter patterns. They attach themselves to C++ classes and forward all communication through FFI. The fact that the C# structure can outlive the C++ structure shows it cannot be a drop-in replacement.

I would love to hear your opinions on this and maybe if this gains enough support, I or someone more knowledgeable than me could take a deeper look and make a proper proposal.

The great thing is that this doesn't necessarily need to be a breaking change immediately. All we'd need to do is do the first part and mark using the default constructor as a deprecated or discouraged approach and warn of the consequences. Then remove it in a breaking way after a few versions to hopefully make the transition easier.