13 Templates [temp]

13.8 Name resolution [temp.res]

13.8.3 Dependent names [temp.dep]

13.8.3.1 General [temp.dep.general]

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Inside a template, some constructs have semantics which may differ from one instantiation to another.
Such a construct depends on the template parameters.
In particular, types and expressions may depend on the type and/or value of template parameters (as determined by the template arguments) and this determines the context for name lookup for certain names.
An expression may be type-dependent (that is, its type may depend on a template parameter) or value-dependent (that is, its value when evaluated as a constant expression ([expr.const]) may depend on a template parameter) as described below.
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A dependent call is an expression, possibly formed as a non-member candidate for an operator ([over.match.oper]), of the form:
postfix-expression ( expression-list )
where the postfix-expression is an unqualified-id and
The component name of an unqualified-id ([expr.prim.id.unqual]) is dependent if
[Note 1: 
Such names are looked up only at the point of the template instantiation ([temp.point]) in both the context of the template definition and the context of the point of instantiation ([temp.dep.candidate]).
— end note]
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[Example 1: template<class T> struct X : B<T> { typename T::A* pa; void f(B<T>* pb) { static int i = B<T>::i; pb->j++; } };
The base class name B<T>, the type name T​::​A, the names B<T>​::​i and pb->j explicitly depend on the template-parameter.
— end example]