Associative Arrays with elements having function type?

[Paul Backus]

On Monday, 3 November 2025 at 21:29:47 UTC, kdevel wrote:
> Yesterday I read
>
>     3. Neither the KeyTypes nor the element types of an 
> associative array
>     can be function types or void.
>
> in <https://dlang.org/spec/hash-map.html>. Does the program 
> below work only accidentally?
>
> ```d
> import std;
>
> void foo () { writeln (__PRETTY_FUNCTION__); }
>
> void bar () { writeln (__PRETTY_FUNCTION__); }
>
> alias fntype = void function ();
>
> fntype [string] routes = [
>       "foo": &foo,
>       "bar": &bar,
>    ];

In this example, `fntype` is not a "function type"; it is a 
"function pointer type."

If you try to use an actual function type, it will fail:

```d
void foo () {}
void bar () {}

alias fntype = typeof(foo);

fntype [string] routes;
// Error: cannot have associative array of `void()`
```