[sv-bc] Mantis 2380: array assignment compatibility

hi BC,

Towards the end of the ballot review, BC pushed across
to EC a few ballot items relating to the assignment
compatibility of unpacked arrays - Mantis 2380 covers
them all.  Although EC didn't have time to consider it
before the May 14 deadline, I would like to get a 
proposal prepared ready for the recirculation.
Although this is now an EC matter, I'd be grateful for
any comments you may have on the following suggestions.

The critical question is whether it is OK (as I and
at least some other members of EC believe) to relax
the existing rules for unpacked array assignment
compatibility so that the elements of the source
and target arrays need only be of ASSIGNMENT COMPATIBLE
types, rather than the current stricter requirement 
that source and target elements be of EQUIVALENT type.
This relaxation would automatically deal with a number
of areas where the LRM is currently self-contradictory
or, at least, confusing (the confusion has been 
compounded by various changes introduced by Mantis
items 1447 and 1702, which were passed some time ago).

Another advantage of this proposed relaxation would be
that it removes a restriction that seems confusing and
unnecessary to many users.  On the other hand, type 
equivalence of elements means that some kinds of 
unpacked array copy operation can be implemented as 
a simple memory block copy; the proposed relaxation 
would require implementations to do an element-by-
element copy.

Thanks in advance for your thoughts on this.
-- 
Jonathan Bromley
Consultant

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