How to check if variable of some type can be of null value?

[Alexey]

On Saturday, 24 July 2021 at 18:10:07 UTC, Alexey wrote:
> I've tried to use ```typeof(t) is cast(t)null```, but compiler 
> exits with error and so this can't be used for checking this 
> issue.
>
> The goal I with to achieve by this check - is to use template 
> and to assign value to variable basing on it's ability to 
> accept null as a value.
>

currently I ended up using ```__traits(compiles, cast(T1)null)``` 
for this check. but don't know is this really semantically 
correct.