Forward declaration inside Function block, no error?

[Jonathan M Davis]

On Sunday, January 6, 2019 11:38:44 AM MST Benjamin Thaut via Digitalmars-d-
learn wrote:
> Today I found a bug in my D code.
>
>
> import std.stdio;
>
> // Type your code here, or load an example.
> void grow()
> {
>      writeln("grow");
> }
>
> void someFunc(bool condition)
> {
>      if(condition)
>      {
>          void grow();
>      }
> }
>
>
> I tried to call the grow function, but accidentially copied the
> return value alongside the function name. I was wondering why
> this code compiles without errors. the "void grow();" becomes a
> no-op. In my opinion this could should not compile. Am I missing
> something here?

It would actually be useful if you could provide prototypes for extern(C)
functions that way (similar to how we can have local imports for modules and
thus avoid affecting the rest of the module), but unfortunately, that
doesn't currently work (even if the function declaration is marked with
static). It would also make sense if it allowed you to provide forward
declarations for nested functions, but that doesn't work either. So, I could
see uses cases where it would theoretically be useful to be able to declare
function prototypes inside of a function, but as it stands, AFAIK, it's
useless. It is arguably a case of "turtles all the way down," but since you
can't then do anything useful with the function prototype, it's currently
pretty pointless.

- Jonathan M Davis