dual-context deprecation

[Paul Backus]

On Monday, 17 May 2021 at 13:47:28 UTC, jmh530 wrote:
> The code below (simplified from my actual problem) generates a 
> warning that member function b "requires a dual-context, which 
> is deprecated".
>
> However when I look at the list of deprecated features [1], I'm 
> not seeing which one this is referring to. Is it a valid 
> deprecation?

See this issue for context:

https://issues.dlang.org/show_bug.cgi?id=5710