How to define property type to Array!struct?

[WebFreak001]

On Wednesday, 15 December 2021 at 11:36:41 UTC, Manfred Nowak 
wrote:
> On Tuesday, 14 December 2021 at 08:28:01 UTC, WebFreak001 wrote:
> [...]
>> Alternatively, remove the template `()` from your `struct 
>> Header`
>
> What is the semantic sense of a template having no parameters?
>
> Although the documentation declares such a template to be 
> syntactically correct, not a single example suggests a meaning.

For functions there is a use-case: they will not be 
compiled/included in the executable until they are actually 
instantiated once.

Additionally for functions that means for libraries they aren't 
usually compiled into the resulting library file, unless they are 
used in the library themself. (only really meaningful when you 
don't distribute the D source or when interoping with other 
languages)

For types similarly, if you have any template instantiations 
inside your templated type, they will not be instantiated or 
compiled, until that template is used at least once in code 
anywhere.

So:
```d
struct Header()
{
     Appender!string name;
}
```
unless Appender!string is used anywhere else in the code, that 
Appender struct will never be initiated, thus no member functions 
will be emitted or compile time will be used, until you 
instantiate the Header struct once.