Extending a bit string

SELECT b'01'::bit(2)::bit(4),

  b'01'::bit(2)::int::bit(4);

 bit  | bit  

------+------

 0100 | 0001

(1 row)

I'd like propose we standardize this a bit. Previously, in version 8 compatibility was broke. From the Version 8 release notes (thanks to Rhodium Toad for the research),

> Casting an integer to BIT(N) selects the rightmost N bits of the integer, not the leftmost N bits as before.

Everything should select the right-most bits, and extend the left-most bits from the docs:

> Casting an integer to a bit string width wider than the integer itself will sign-extend on the left.

That makes sense to me. Intergers sign-extend on the left, and the behavior is currently undefined for bit->bit extensions. What say you?