Has someone encountered similar issues with -cov?

[Andrei Alexandrescu via Digitalmars-d]

On 07/02/2016 11:15 AM, Guillaume Boucher wrote:
> Your function does redundant work.  E.g. opCast!(int, ubyte) should not
> require any checks.  I also don't understand why opCast!(int, ubyte) is
> not allowed.

It's an adapted fragment from a larger function that handles other cases 
separately. -- Andrei