Implicit instantiation of parameterless templates

[Piotr Szturmaj]

Paulo Pinto wrote:
> On Friday, 5 October 2012 at 12:01:30 UTC, Piotr Szturmaj wrote:
>> Java and C# with their generics can do the following:
>>
>> class List { }
>> class List<T> { }
>>
>> List list = new List();
>> List<int> intList = new List<int>();
>>
>> In D similar code can't work because we can't have both a type and a
>> template with the same name. So this code must be rewritten to:
>>
>> class List(T = Variant) { }
>>
>> List!() list = new List!();
>> List!int intList = new List!int;
>>
>> When template name is used as a type and it can be instantiated with
>> no parameters it could be automatically rewritten to List!() by the
>> compiler. That code would then look like this:
>>
>> List list = new List;
>> List!int intList = new List!int;
>>
>> The question is... is it possible to change D's behaviour to avoid
>> awkward !() template parameters _without_ breaking backward
>> compatibility?
>
> Why to you need this?

For convenience. In the above example, List without parameters could 
handle any value (as Variant), but I can always specialize it for some 
type. List (which would be List!()) would then become a shortcut to 
List!Variant.

> Java and C# only allow this type of code due to backwards compatibility,
> because their first version did not allow for generics, and their
> creators did not want to force everyone to recode their code bases.

Yes, but it's more convenient to write List than List<Object>. And in D: 
List vs List!().