This example given for the 3-arg version of dirEntries works as expected:

---
foreach (string name; dirEntries(".", "*.d", SpanMode.breadth))
{
    writeln(name);
}
---

But when modified to use the 4-arg version, like so:

---
import std.stdio, std.file;

void main()
{
    foreach (string name; dirEntries(".", "*.d", SpanMode.breadth))
    {
        writeln(name);
    }
}
---

It fails with this error:

fail.d(7): Error: cannot implicitly convert expression (__r13.front()) of type D
irEntry to string