Associative array literal: length wrong when duplicate keys found

[Ivan Kazmenko via Digitalmars-d-learn]

Hi.

I wanted to check whether a few variables of the same type are 
all distinct, in a quick and dirty way.  I tried to do it similar 
to Python's "len(set(value_list)) == len(value_list)" idiom by 
using an associative array (AA).  At this point, I found out that 
when initializing the AA with a literal, the length is the number 
of keys given, regardless of whether some of them were the same.

A minimized example:

-----
import std.stdio;
void main () {
	auto aa = [1 : 2, 1 : 3];
	writeln (aa.length, " ", aa); // 2 [1:3, ]
}
-----

See, the length is 2, but iteration over aa yields only one 
key:value pair.  Also, note the comma which is a sign of internal 
confusion as well.

My question is, what's the state of this?  Is this a bug?  Or 
should it be forbidden to have such an initializer?  Or maybe it 
is a feature with some actual merit?

Ivan Kazmenko.