Issue when converting between multiple data types

To joysb: it was constructive criticism, and I think it does help. Making lsb, msb and destination_register unsigned instead of std_logic already removes a lot of conversions in the code, and makes it easier to read and debug.

To alegomaster: you are on the right track, using a loop is the best (only?) way to do concatenation of vectors with dynamic size. You just overlooked something:

31 to 0

this range is empty. It should either be 0 to 31 or 31 downto 0. Don't worry, we all make this mistake at least once ;) Quartus has probably put a warning about this, but it writes so many warnings it is easy to miss it. But hopefully it should synthesize correctly after this modification.