How to append range to array?

[Vladimir Panteleev via Digitalmars-d-learn]

int[] arr = [1, 2, 3];
auto r = iota(4, 10);
// ???
assert(equal(arr, iota(1, 10)));
Hopefully in one GC allocation (assuming we know the range's 
length).

I tried std.range.primitives.put but its behavior seems a little 
mysterious:

This compiles but asserts at runtime:

int[] arr = [1, 2, 3];
arr.put(iota(4, 10));

And this is even weirder, can you guess what it will print?

int[] arr = [1, 2, 3];
arr.put(4);
writeln(arr);