Bug Nested SerializeReference in a wrapper, freezes and crashes the editor.

Just posting in case someone encounters something like this on 2020.2+. Bug report number: 1317913


Minimal example, just add an "AWrapper" to a monobehaviour:

Code (CSharp):

1. using System;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5.  
6. //Testing interfaces with SerializeReference
7. public interface IA {}
8. public interface IB {}
9.  
10.  
11. // ======================== //
12. //Concrete implementations
13. //Appending to BWrappers in the inspector will freeze the editor, it will then consume all memory until crash.
14. [Serializable]
15. public class AImpl : IA {
16.     public List<BWrapper> BWrappers;
17. }
18.  
19. [Serializable]
20. public class BImpl : IB {}
21. // ======================== //
22.  
23.  
24. // ======================== //
25. //Wrappers
26. [Serializable]
27. public class AWrapper { // hierarchy starts with an instance of this
28.     [SerializeReference]
29.     public IA IAImpl = new AImpl();
30. }
31. [Serializable]
32. public class BWrapper {
33.     [SerializeReference]
34.     public IB IBImpl;
35. }
36. // ======================== //
37.  
38.  
39. // ======================== //
40. /* SEMI WORKING EXAMPLES
41. // Initially works, but if BWrappers length becomes 0 in editor and is appended again, causes the freeze.
42. [Serializable]
43. public class AImpl : IA {
44.     public List<BWrapper> BWrappers;
45.  
46.     public AImpl() {
47.         BWrappers = new List<BWrapper> {
48.             new BWrapper {
49.                 IBImpl = new BImpl()
50.             }
51.         };
52.     }
53. }
54.  
55. // Initially works as above, but if appended to, BWrapper constructors are not called.
56. [Serializable]
57. public class AImpl : IA {
58.     [SerializeReference]
59.     public List<BWrapper> BWrappers;
60.  
61.     public AImpl() {
62.         BWrappers = new List<BWrapper> {
63.             new BWrapper {
64.                 IBImpl = new BImpl()
65.             }
66.         };
67.     }
68. }
69. */
70. // ======================== //
71.  
72.