BUG #7620: array_to_json doesn't support heterogeneous arrays

The following bug has been logged on the website:

Bug reference:      7620
Logged by:          Greg Hazel
Email address:      ghazel@gmail.com
PostgreSQL version: 9.2.1
Operating system:   Amazon Linux
Description:        =


array_to_json(ARRAY['foo', 100, true]) complains because arrays can't have
mixed types, but json arrays can.

So, it's not possible to form a heterogeneous json array, when this is often
desired.