Re: Has someone encountered similar issues with -cov?

[Guillaume Boucher via Digitalmars-d]

On Saturday, 2 July 2016 at 12:26:34 UTC, Andrei Alexandrescu 
wrote:
How would you reshape this? It's important that the call to 
hook is physically at the end of the function and issued just 
in that place, and that the code does not do any redundant work.

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.

The following code should do the same as yours, but without 
unnecessary checks:

U opCast(U, T)(T payload)
{
        import std.traits;
        enum Tsizeof = is(T==bool) ? 0 : T.sizeof;
        enum Usizeof = is(U==bool) ? 0 : U.sizeof;
        enum noCheck = isUnsigned!T == isUnsigned!U && Tsizeof <= 
Usizeof ||
                       isUnsigned!T && Tsizeof < Usizeof;
        enum checkPayload = !isUnsigned!T && isUnsigned!U;
        enum checkResult = isUnsigned!T && !isUnsigned!U;
        static if (checkResult)
        {
                static assert(U.sizeof <= T.sizeof);  // I don't 
understand this
        }

        if (!checkPayload || payload >= 0)
        {
                auto result = cast(U) payload;
                if (noCheck || result == payload && (!checkResult 
|| result >= 0))
                        return result;
        }
        return hook!U(payload);
}