Prefer Signed or Unsigned in D?

[Dominikus Dittes Scherkl via Digitalmars-d-learn]

On Wednesday, 2 September 2015 at 09:47:16 UTC, BBasile wrote:
> On Tuesday, 1 September 2015 at 23:06:50 UTC, John Carter wrote:
>> C/C++ discussion here....
>>
>>    http://blog.robertelder.org/signed-or-unsigned-part-2/
>>
>> D rules here...
>>
>>    http://dlang.org/type.html#integer-promotions
>
> It depends on the context.
>
> You should take care of blending signed and unsigned:
> comparison error, a is > b but...
> ---
> uint a = 1;
> int b = -1;
> assert(a < b); // does not throw
> ---
>
> You should take care to the index type in a loop:
> loop that doesn't run at all because of an infered unsigned 
> index...
> ---
> auto array = new int[](8);
> for (auto i = array.length - 1; i > -1; i--)
>     array[i] = 8;
> assert(array[0] == 0); // does not throw
> ---

I wish the following would be the standard D behaviour (for T == 
U or if floats are involved neither C nor D have a problem)):

int opCmp(T, U)(const(T) a, const(U) b) pure @safe @nogc nothrow
    if(isIntegral!T && isIntegral!U && !is(Unqual!T == Unqual!U))
{
    alias C = CommonType!(T, U);
    static if(isSigned!T && isUnsigned!U && T.sizeof <= U.sizeof)
       return (a < 0) ? -1 : opCmp(cast(U)a, b);
    else static if(isUnsigned!T && isSigned!U && T.sizeof >= 
U.sizeof)
       return (b < 0) ? 1 : opCmp(a, cast(T)b);
    else return opCmp(cast(C)a, cast(C)b);
}

this is really almost equally fast, but always correct.