How do I initialize a templated constructor?

[Steven Schveighoffer]

On 8/8/22 1:38 AM, rempas wrote:
> In the following struct (as an example, not real code):
> 
> ```
> struct TestArray(ulong element_n) {
>    int[element_n] elements;
> 
>    this(string type)(ulong number) {
>      pragma(msg, "The type is: " ~ typeof(type).stringof);
>    }
> }
> ```
> 
> I want to create it and be able to successfully initialize the template 
> parameters
> of the constructor but until now, I wasn't able to find a way to 
> successfully do
> that. Is there a way you guys know?  I have tried the following:
> 
> ```
> void main() {
>    // Doesn't work
>    auto val = TestArray!(10, "int")(60);
> 
>    // Doesn't work either
>    auto val = TestArray!(10).TestArray!("int")(60);
> 
>    // Neither this works....
>    auto val = TestArray!(10).this!("int")(60);
> }
> ```
> 
> As with every question I make, the solution must be "betterC" compatible 
> so I can use it.
> Thanks a lot!

You cannot explicitly specify template parameters for constructors.

The only true solution is to use a factory function:

```d
TestArray!T testarray(string s, T)(T val) {
    ... // code that depends on s here
    return TestArray!T(...) // call ctor here.
}
```

-Steve