^^ limitation

[Tyro[17]]

I believe the following two lines of code should produce the same 
output. Is there a specific reason why doesn't allow this? Of course the 
only way to store the result would be to put in into a BigInt variable 
or convert it to string but I don't that shouldn't prevent the compiler 
from producing the correct value.

(101^^1000).to!string.writeln;
(BigInt(101)^^1000).writeln;
Regards,
Andrew