Catching exception with `when` clause will not work as expected when using IL2CPP.

Here's the code which repeat the bug:

Code (CSharp):

1.     private void TestCatchWhen()
2.     {
3.         // Condition in when clause evaluates to true, everything is all right.
4.         // Always output "CustomException: code = 0".
5.         CatchException(0);
6.  
7.         // Condition in when clause evaluates to false, something is going wrong.
8.         // When using MONO, the output is "Exception: This is custom exception!"
9.         // When using IL2CPP, the output is "** Should not reach here **"
10.         CatchException(1);
11.     }
12.  
13.     private void CatchException(int code)
14.     {
15.         try
16.         {
17.             try
18.             {
19.                 throw new CustomException("This is custom exception!") { Code = code };
20.             }
21.             catch (CustomException ce)
22.             when (ce.Code == 0) // This will NOT work as expected if the condition evaluates to false when using IL2CPP!
23.             {
24.                 Debug.LogErrorFormat("CustomException: code = {0}", ce.Code);
25.             }
26.             catch (Exception e)
27.             {
28.                 Debug.LogErrorFormat("Exception: {0}", e.Message);
29.             }
30.         }
31.         catch (Exception)
32.         {
33.             Debug.LogError("** Should not reach here **");
34.         }
35.     }

The definition of CustomException is:

Code (CSharp):

1. public class CustomException : Exception
2. {
3.     public int Code { get; set; }
4.  
5.     public CustomException(string message) : base(message)
6.     { }
7. }

The expected behaviour of

CatchException(1)

is that it always outputs "Exception: This is custom exception!".

 

By the way, I'm using Unity 2019.4.11f1.
Here's the project which repeat the bug.

 

https://www.jacksondunstan.com/articles/4702

Seems old.

 

This article is very helpful. Thx.