Check this:
http://dpaste.dzfl.pl/ebbb3ebac60e

It doesn't give any error or warning. And writeln seems confused (do you see that "," at the end?)

On Thursday, 5 November 2015 at 08:55:10 UTC, Andrea Fontana wrote:
> Check this:
> http://dpaste.dzfl.pl/ebbb3ebac60e
>
> It doesn't give any error or warning. And writeln seems confused (do you see that "," at the end?)

I am sure the coder of writeln was lazy to prevent putting ", " after last item. You can report it as a bug I guess.

On Thursday, 5 November 2015 at 09:27:35 UTC, tcak wrote:
> On Thursday, 5 November 2015 at 08:55:10 UTC, Andrea Fontana wrote:
>> Check this:
>> http://dpaste.dzfl.pl/ebbb3ebac60e
>>
>> It doesn't give any error or warning. And writeln seems confused (do you see that "," at the end?)
>
> I am sure the coder of writeln was lazy to prevent putting ", " after last item. You can report it as a bug I guess.

Not really: it appears only if array has duplicated keys.

Anyway: are duplicated keys on declaration allowed?

On Thursday, 5 November 2015 at 10:04:02 UTC, Andrea Fontana wrote:
> Anyway: are duplicated keys on declaration allowed?

IMHO This should at least be a warning.

On Thursday, 5 November 2015 at 08:55:10 UTC, Andrea Fontana wrote:
> Check this:
> http://dpaste.dzfl.pl/ebbb3ebac60e
>
> It doesn't give any error or warning. And writeln seems confused (do you see that "," at the end?)

This is an outright bug, please report on issues.dlang.org:

void main()
{
    import std.stdio : writeln;
    ["key": 10, "key" : 20, "key" : 30].length.writeln;
    ["key" : 30].length.writeln;
}

Prints:
3
1

https://issues.dlang.org/show_bug.cgi?id=15290

On Thursday, 5 November 2015 at 10:04:02 UTC, Andrea Fontana wrote:
> Anyway: are duplicated keys on declaration allowed?

They shouldn't be...

On Thursday, 5 November 2015 at 13:08:20 UTC, Adam D. Ruppe wrote:
> On Thursday, 5 November 2015 at 10:04:02 UTC, Andrea Fontana wrote:
>> Anyway: are duplicated keys on declaration allowed?
>
> They shouldn't be...

Why? I'll admit it is something I've never even thought of using, but every language I know (just tested with python, lua, scheme and js) accepts it and as far as I can tell from a user perspective boils

    auto aa = ["a":10, "b", 42, "a":20];

down to:

     int[string] aa;
     aa["a"] = 10;
     aa["b"] = 42;
     aa["a"] = 20;

This is deterministic and could allow one to build an associative array through a mixin for example while still giving default values.

As I said, it's not something I've used but I think we should consider it.

On Friday, 6 November 2015 at 14:28:53 UTC, cym13 wrote:
>     auto aa = ["a":10, "b", 42, "a":20];

This should read    auto aa = ["a":10, "b":42, "a":20];  of course.