Nested functions should be exempt from sequential visibility rules

[Don Clugston]

On 03/04/12 07:38, Nick Sabalausky wrote:
> Regarding this:
>
> http://d.puremagic.com/issues/show_bug.cgi?id=790
>
> I submit that nested functions should be exempt from the usual sequential
> visibility rules. (Therefore, mutually recursive nested functions would
> become possible.)
>
> Or at the very *least*, this horrific C-like workaround should be possible:
>
> void foo()
> {
>      void b();
>      void a() {...};
>      void b() {...};
> }
>
> ...Flame away! ;)
>

This is asking for a complicated special case. In global scope, order of 
declarations doesn't matter. In function scope, order of declarations 
always matters.
If you have type inference of function returns, things can get nasty:

void foo()
{
      auto b() { return a(); }
      X x = whatever;
      auto a() { return x; }
}
Now b actually depends on the declaration of x. So it's not enough to 
say that only function declarations are immune to ordering rules.
Furthermore, any declaration before x, which calls b(), is using x even 
though x hasn't been initialized (or even declared) yet. Suddenly all 
kinds of horrible situations become possible, which could never happen 
before.

In general, allowing forward references inside a function is far, far 
more difficult than in global scope. There are very many more special 
cases. Allowing it in global scope is quite complicated enough.

You can always use a delegate, if you want recursive nested functions.