Checking template parameter types of class

[tcak via Digitalmars-d-learn]

On Monday, 25 May 2015 at 04:07:06 UTC, Jonathan M Davis wrote:
> On Monday, May 25, 2015 03:42:22 tcak via Digitalmars-d-learn 
> wrote:
>>
>> Well, if I do not check the line number of error, this happens.
>> It was giving error on the line of creating a new instance.
>>
>> Line 243: auto fileResourceList = new shared FileResourceList( 
>> 2
>> );
>>
>> main.d(243): Error: class main.FileResourceList(T) if (is(T :
>> FileResource)) is used as a type
>
> shared(FileResourceList) is not implicitly convertible to 
> FileResource. It
> may be implicitly convertible to shared(FileResource), but not
> FileResource). Code that uses shared usually has to be written 
> specifically
> for shared. Also, any time that you construct a templated type, 
> you have to
> provide the template argument. IFTI (implicit function template
> instantiation) doesn't work with constructors. To make that 
> work, you need a
> wrapper function - e.g.
>
> auto resource(T)(T t)
> {
>     return new Resource!T(t);
> }
>
> So, I suspect that you're either running into problems, because 
> you're using
> shared, and Resource's template constraint requires non-shared, 
> and/or
> because you aren't explicitly instantiating Resource with a 
> template
> argument.
>
> - Jonathan M Davis

Nah. Its all about giving the T value on object creation.

auto fileResourceList = new shared FileResourceList!FileResource( 
2 );

Then it works. The error message is not indicating directly this, 
though logically it is still correct.