Calling nested function before declaration

[Jonathan via Digitalmars-d]

This code fails to compile: ("undefined identifier fun")
void main() {
    fun();
    void fun() {}
}
Having the call after the declaration works:
void main() {
    void fun() {}
    fun();
}

Is this how it is intended to work?

It seems goofy that this works:
void main() {
    void fun2() {}
    void fun() {
         fun2()
    }
    fun();
}

But this fails to compile: ("undefined identifier fun2")
void main() {
    void fun() {
         fun2()
    }
    void fun2() {}
    fun();
}

What if I wanted this?
void main() {
    void fun2() {fun();}
    void fun() {fun2();}
    fun();
}

I can't see how the current behavior is at all better or to be 
preferred unless it is faster to compile?  What is the reason for 
it being how it is?