Strange appender behavior

[Andrea Fontana]

On Wednesday, 13 March 2019 at 13:03:27 UTC, tchaloupka wrote:
> Is this expected?:
>
> ```
> import std.stdio;
> import std.algorithm;
> import std.array;
>
> void main()
> {
>     auto d = Appender!string();
>     //auto d = appender!string(); // works
>
>     string[] arr = ["foo", "bar", "baz"];
>     arr.joiner("\n").copy(d);
>     writeln(d.data);
> }
> ```
>
> Using Appender outpust nothing, using appender works ok.

It sounds like a bug. If you use Appender!string(null) it works 
fine. Probably a problem with _data init?