Memory allocation faile on string concat

[Xie]

Can't run a simple program. What's wrong, GC?

import std.stdio;
import std.date;

void f0()
{
        wstring a[];

        foreach(i; 0 .. 100_000_000)
        {
                a ~= " "w;
        }
}

void main()
{
        auto r = benchmark!(f0)(1);
        writeln(r, "ms");
}

DMD 2.047