class template specialization and inheritance

[Bill Baxter]

mki wrote:
> I don't see why the original
> class C(TT:A!(T))
> shouldn't be legal.
> 
> in C++ style syntax I would have
> 
> //primary template
> template<typename T>
> class C {};
> 
> //template specialization of C
> template<typename TT, typename T>
> class C<TT:A<T> > ... ;
> 
> (Of course this isn't legal either, because C++ doesn't have the colon-syntax.)
> 
> Now D does away with primary templates, so the first part can be skipped completely in D.
> Furthermore, D does not need the line
> template<typename TT, typename T>
> because the template parameters of the specialization can be completely deduced from the expression C<TT:A<T> >. All undeclared symbols are template parameters.
> 
> So to my understanding,
> C(TT:A(T))
> should be legal D and should have the sense I indicated with the C++ style syntax above. Also notice that there is no compiler error message on this expression.

 From http://www.digitalmars.com/d/1.0/template.html
"""
Deduction from a specialization can provide values for more than one 
parameter:

template Foo(T: T[U], U)
{
     ...
}

Foo!(int[long])  // instantiates Foo with T set to int, U set to long
"""

But (for D1 at least) that doesn't work with argument deduction:

void fBaz(T: T[U], U)(T[U] x) {
     writefln("typeof(T)=",typeid(T)," typeof(U)=",typeid(U));
}
...
int[long] z;
fBaz(z);

 >> partialifti.d(24): template partialifti.fBaz(T : T[U],U) 
specialization not allowed for deduced parameter T


> For my programming purpose, the important thing is that C(TT:A(T)) is a specialization of C(T), but the suggested C(TT:A(T),T) is _not_.

According to the documentation D thinks it is.  Do you have evidence to 
the contrary?

> For this reason, I really need the first variant, and not the second one.
 >
> I would like to hear further opinions on this. I my understanding correct, or not?

Sadly the argument deduction (IFTI) implementation is not very complete. 
  It only works in very specific situations.

--bb