[cfe-dev] Error name lookup in template dependant base class

[John McCall]

On Dec 14, 2010, at 2:01 PM, John McCall wrote:
> On Dec 14, 2010, at 1:33 PM, Adrien Chauve wrote:
>> I don't think the problem is ADL here. The name of the function call is a dependant name, so the unqualified lookup is delayed until instanciation: it's not ADL, it's just delayed ordinary lookup. At instanciation time and when all explicit template specializations are available, lookups can be done in the base class to find members.
> 
> Well, no, they can't.  This is what we're all trying to explain.  The standard is extremely explicit about this:
> 
> C++ [temp.dep.res]p1:
>  In resolving dependent names, names from the following sources are considered:
>  — Declarations that are visible at the point of definition of the template.
>  — Declarations from namespaces associated with the types of the function arguments both from the instantiation context and from the definition context.

This is actually not the part of the standard I meant to quote, although it does apply.  The better quote is [temp.dep.candidate]p1:

  For a function call that depends on a template parameter, the candidate functions are found using the usual lookup rules except that:
  — For the part of the lookup using unqualified name lookup or qualified name lookup, only function declarations from the template definition context are found.
  — For the part of the lookup using associated namespaces, only function declarations found in either the template definition context or the template instantiation context are found.

John.