Special Type Challenge

[Jonathan Marler via Digitalmars-d]

I'm wondering if the following is possible in D.  I tried and 
failed but maybe someone else will be able to pull it off.

// Challenge: Create a type named "Byte" that,
//   1. Uses 1 byte of memory
//   2. Can be used as an argument to a non-template function
//   3. Handles implicit conversion from any 1-byte type
//   4. Compiles and passes the following unittest
unittest
{
   Byte b;

   b = 0;
   b = 1;
   b = 255;
   b = -256;

   b = 'a';
   b = cast(const char)'a';
   b = cast(immutable char)'a';
   b = cast(byte)1;
   b = cast(const byte)1;
   b = cast(immutable byte)1;
   b = cast(ubyte)1;
   b = cast(const ubyte)1;
   b = cast(immutable ubyte)1;

   Byte echo(Byte b)
   {
     return b;
   }
   b = echo('a');
   b = echo(cast(const char)'a');
   b = echo(cast(immutable char)'a');
   b = echo(cast(byte)1);
   b = echo(cast(const byte)1);
   b = echo(cast(immutable byte)1);
   b = echo(cast(ubyte)1);
   b = echo(cast(const ubyte)1);
   b = echo(cast(immutable ubyte)1);

   Byte[] barr;

   barr = "teststring";
   barr = [0,1,2,3];
}