I wrote:
> Not entirely sure what to make of this. It occurs to me that the "it
> breaks immutability" argument might apply to array_nulls, though I've
> not done any legwork to confirm or disprove that. If it doesn't apply,
> though, I'm leaning to the position that there's no reason to remove
> array_nulls.
OK, I went and looked. Array_nulls is consulted only in array_in(),
which is marked stable (and would need to be so marked even without
this consideration, since the array element type's input function
might only be stable). So it's not breaking any rules.
regards, tom lane