BUG #8399: inconsistent input of multidimensional arrays

The following bug has been logged on the website:

Bug reference:      8399
Logged by:          Alexey Borzov
Email address:      borz_off@cs.msu.su
PostgreSQL version: 9.3rc1
Operating system:   irrelevant
Description:

PostgreSQL documentation states:


"Multidimensional arrays must have matching extents for each dimension. A
mismatch causes an error..."


This is not completely true:
postgres=# select cast('{{1,2}, {3}}' as integer[]);
ERROR:  multidimensional arrays must have array expressions with matching
dimensions
LINE 1: select cast('{{1,2}, {3}}' as integer[]);
                    ^
postgres=# select cast('{{1}, {2,3}}' as integer[]);
       int4
------------------
 {{1,NULL},{2,3}}
(1 row)


Trying to use an array constructor yields an expected error in both cases.


Confirmed on 9.3rc1 and 9.0.13