Passing iterators into functions

[repr-man]

I have the code:

int[5] a = [0, 1, 2, 3, 4];
int[5] b = [5, 6, 7, 8, 9];
auto x = chain(a[], b[]).chunks(5);
writeln(x);

It produces a range of slices as is expected: [[0, 1, 2, 3, 4], 
[5, 6, 7, 8, 9]]

However, when I define a function as follows and pass in the 
result of the chain iterator:

auto func(R)(R r, size_t width)
if(isRandomAccessRange!R)
{
     return r.chunks(width);
}

void main()
{
     int[5] a = [0, 1, 2, 3, 4];
     int[5] b = [5, 6, 7, 8, 9];
     auto x = func!(int[])(chain(a[], b[]), 5);
     writeln(x);
}

It gives me an error along the lines of:
Error: func!(int[]).func(int[] r, ulong width) is not callable 
using argument types (Result, int)
        cannot pass argument chain(a[], b[]) of type Result to 
parameter int[] r

I was hoping it would return the same result as the first program.

This seems to have to do with the fact that all iterators return 
their own unique type.  Could someone help me understand the 
reason behind this design and how to remedy my situation?