BitArray - incomplete implementation?

[Laeeth Isharc via Digitalmars-d-learn]

To avoid confusion, the below is the code that fits the error 
message:

import std.bitmanip;
import std.stdio;
import std.array;
import std.range:chain;

void test()
{
	int[] a=[1,2,3,4,5];
	int[] b=[5,4,3,2,1];
	int[] c = chain(a,b).array; // chain two arrays of int
	writefln("%s",c);
}

void test2()
{
	BitArray a;
	a.init([1,0,1,0]);
	BitArray b;
	b.init([0,1,0,1]);
	BitArray[] d;
	d~=a;
	d~=b;
	BitArray[] c=chain(a,b).array; // cannot chain two bitarrays
	BitArray[] c=chain([a],[b]).array; // cannot chain two bitarrays
	BitArray[] e=chain(d,d).array; // cannot chain two arrays of 
bitarrays
	writefln("%s",c);
}

int main(string[] args)
{
	test();
	test2();
	return 1;
}