Strange closure behaviour

[Emmanuelle]

Take a look at this code:

---
import std.stdio;

void main()
{
     alias Func = void delegate(int);

     int[][] nums = new int[][5];
     Func[] funcs;
     foreach (x; 0 .. 5) {
         funcs ~= (int i) { nums[x] ~= i; };
     }

     foreach (i, func; funcs) {
         func(cast(int) i);
     }

     writeln(nums);
}
---

(https://run.dlang.io/is/oMjNRL)

The output is:

---
[[], [], [], [], [0, 1, 2, 3, 4]]
---

Personally, this makes no sense to me. This is the result I was 
expecting:

---
[[0], [1], [2], [3], [4]]
---

Why is it "locking" the bound `x` to the last element? It seems 
like the compiler is overwriting the closure for `x`, somehow. 
So, I'm wondering why D is doing that. Is it a compiler bug? Or 
is this the expected behaviour?