Even stricter implicit conversions between vectors

[Paolo Bonzini]

>>> Assuming I understand the proposal properly, this sounds to me like 
>>> it amounts reversing the change  we experienced in the Apple GCC 
>>> from 3.3 -> 4.0.  Type checking became a lot more lax for us in 4.0.
>>
>> This was a bug and has been fixed recently.  I cannot recall if the 
>> fix has been backported all the way up to 4.0.
>
> Which fix are you thinking of here?  My previous one for rejecting
> implicit conversions between vector types between differing numbers
> of subparts hasn't been submitted as a patch yet, but has pretty much
> been approved in principle.
Oops, yes, that was it.  Does it have a PR number?

Paolo