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];
}