template auto instantiation when parameters empty

[Steven Schveighoffer via Digitalmars-d-learn]

On 5/5/16 12:10 AM, Erik Smith wrote:
> I want to have a struct template auto instantiate when the template
> parameters are defaulted or missing.  Example:
>
> struct Resource(T=int) {
>      static auto create() {return Resource(null);}
>      this(string s) {}
> }
>
> auto resource = Resource.create;
>
> As a plain struct it works, but not as a template:
>
> struct Resource {   // works
> struct Resource() {  // fails
> struct Resource(T=int) {  // fails
>
> At the call site, this works, but I'm hoping for a few less symbols:
>
> auto resource = Resource!().create;
>
> Any ideas?

Instead of static method, use an external factory method:

static auto createResource(T = int)()
{
    return Resource!T(null);
}

And I wouldn't bother with making Resource's T have a default, as you'd 
still have to instantiate it with Resource!() to get the default.

-Steve