dup method const or not?

[mta`chrono]

Okay, what about this hack?

---
import std.bitmanip;
import core.stdc.string;

void main()
{
    const(BitArray) foo;
    BitArray bar;

    bar.len = foo.len;
    bar.ptr = foo.ptr[0 .. foo.dim].dup.ptr;
}
---