non-constant error for module AA"s

[Andrej Mitrovic]

Is this a bug?

import std.stdio;

string[string] values = ["abc":"abc", "def":"def"];

void main()
{
    string[string] values2 = ["abc":"abc", "def":"def"];
}


test.d(3): Error: non-constant expression ["abc":"abc","def":"def"]

What's non-constant about that expression?