to! converting 1D to 2D array

[ed]

Hi All,

I am trying to convert a 1D array to a 2D array using to! and was 
wondering if someone could explain to me why this first example 
works but the second example does not compile:

Example 1:
~~~
import std.conv;
long[4] a=[1,2,3,4];
int[2][2] b = to!(int[])(a);
assert(b == [[1,2],[3,4]]);
~~~~

Example 2:
~~~
import std.conv;
long[4] a=[1,2,3,4];
int[2][2] b;
b = to!(int[])(a);
assert(b == [[1,2],[3,4]]);
~~~~
Error: cannot implicitly convert expression (to(a[])) of type 
int[][] to int[2][].

It's like the ReturnType in to!()() for Example 1 and Example 2 
is different. Is  this the case and why would it be so? If not, 
what is happening here?

Thanks,
ed