Reactiveui: [Feature Request] Fody does not support property initializers (C# 6+) on generic classes

Created on 21 May 2020 · 5Comments · Source: reactiveui/ReactiveUI

This is an odd one but is extremely easy to reproduce:

Create a new project, i.e. a console app.
Create a generic class derived from ReactiveObject.
Add a property with an auto-property initializer (a feature of C# 6) to the class.
Decorate the property with the [Reactive] attribute.
Construct the class and run the code.

Here's the code:

// This class throws an exception
public class GenericFoo<T> : ReactiveObject
{
    [Reactive] public object FooObj { get; set; } = new object();
}

// This class works fine
public class Foo : ReactiveObject
{
    [Reactive] public object FooObj { get; set; } = new object();
}

You can construct the Foo class but when ctoring the GenericFoo you will get an exception. For example, running the code:

var f2 = new GenericFoo<object>();

Throws the following runtime exception:

System.MissingFieldException: 'Field not found: 'FodyBug.GenericFoo`1.k__BackingField'.'

Workaround:
The workaround is not to use auto-property initializer and just initialize the property in ctor. This only happens in generic classes. This took me a few hours to figure out since I started with a regular class, made it generic and was suddenly getting the strange exception.

The .Net Core 3.1 console project to reproduce the issue:
FodyBug.zip

Tested on:
Windows 10 x64, Visual Studio 2019 v16.5.5, RxUI/Fody v11.4.1, .Net Core 3.1

Personal note
It's kind of a strange notion, to use these initializers on Fody-ed properties in the first place, but it does work on non-generic classes which is pretty awesome actually. Purely based on that I'm guessing it can work just the same on generic classes which is why I labeled this as a bug.

feature request reactiveui-fody

Source