I was updating a library lately to their latest bits (PostSharp Cache if you are curious) and this new version started to return compilation warnings for code that was compiling for years. But when you really look at it, it totally makes sense. In short, I was using cache on a method returning an integer (a function) but that was also returning one of the arguments ByRef (ref in C#).

Time to find a workaround because I do not want to go back to a previous version, and I want my code to compile.

You can read the full article from https://www.emoreau.com/Entries/Articles/2020/05/Using-ValueTuple-in-Net.aspx.