Cannot check function address

[frame]

On Wednesday, 25 May 2022 at 02:42:26 UTC, Steven Schveighoffer 
wrote:

> Just to be pedantic, you tried that call in the *exact place* 
> the assert is failing to compile? D can be weird/surprising 
> about name lookups.

Yes, of course ;-)


> try:
>
> pragma(msg, typeof(fun));

Outputs:
```
extern (C) void function(...)
```

>
> If I do:
>
> ```d
> extern(C) void foo(string) {}
>
> pragma(msg, typeof(foo));
> pragma(msg, typeof(&foo));
> ```
>
> I get:
>
> extern (C) void(string param)
> extern (C) void function(string param)
>
> The first is a function (yes, they have a type), and the latter 
> is a function pointer.

But the compiler would complain if I call it as a type? And how 
could it call it later without an address to it - this works.

> D should never call a function pointer without parentheses.

I'm very good in finding weird bugs ;-) Unfortunately, I cannot 
make an example. I already tried some changes/simplifications but 
cannot reproduce it outside the project.

But how can I help the compiler to use it as correct type? On 
invocation with arguments all works fine, but checking if the 
pointer is not null fails. It not even works with an assignment. 
Could some `static if()` maybe help or some asm trick?