13 Templates [temp]

For a function template specialization, a member function template specialization, or a specialization for a member function or static data member of a class template, the point of instantiation of the specialization is the point of instantiation of the enclosing specialization if

• (1.1)
  the specialization is implicitly instantiated because it is referenced from within another template specialization and
• (1.2)
  the context from which it is referenced depends on a template parameter.

Otherwise, the point of instantiation for such a specialization immediately follows the namespace scope declaration or definition that refers to the specialization.

If a function template or member function of a class template is called in a way which uses the definition of a default argument of that function template or member function, the point of instantiation of the default argument is the point of instantiation of the function template or member function specialization.

For a noexcept-specifier of a function template specialization or specialization of a member function of a class template, the point of instantiation of the noexcept-specifier is the point of instantiation of the specialization that requires it if

• (3.1)
  the noexcept-specifier is implicitly instantiated because it is needed by another template specialization and
• (3.2)
  the context that requires it depends on a template parameter.

Otherwise, the point of instantiation for such a noexcept-specifier immediately follows the namespace scope declaration or definition that requires the noexcept-specifier.

For a class template specialization, a class member template specialization, or a specialization for a class member of a class template, the point of instantiation is immediately before the point of instantiation of the enclosing template if

• (4.1)
  the specialization is implicitly instantiated because it is referenced from within another template specialization,
• (4.2)
  the context from which the specialization is referenced depends on a template parameter, and
• (4.3)
  the specialization is not instantiated previous to the instantiation of the enclosing template.

Otherwise, the point of instantiation for such a specialization immediately precedes the namespace scope declaration or definition that refers to the specialization.

If a virtual function is implicitly instantiated, its point of instantiation is immediately following the point of instantiation of its enclosing class template specialization.

An explicit instantiation definition is an instantiation point for the specialization or specializations specified by the explicit instantiation.

A specialization for a function template, a member function template, or of a member function or static data member of a class template may have multiple points of instantiations within a translation unit, and in addition to the points of instantiation described above,

• (7.1)
  for any such specialization that has a point of instantiation within the declaration-seq of the translation-unit, prior to the private-module-fragment (if any), the point after the declaration-seq of the translation-unit is also considered a point of instantiation, and
• (7.2)
  for any such specialization that has a point of instantiation within the private-module-fragment, the end of the translation unit is also considered a point of instantiation.

A specialization for a class template has at most one point of instantiation within a translation unit.

A specialization for any template may have points of instantiation in multiple translation units.

If two different points of instantiation give a template specialization different meanings according to the one-definition rule, the program is ill-formed, no diagnostic required ([ifndr:temp.point.diff.pt.diff.meaning]).

For the compound-statement of an expansion-statement ([stmt.expand]), the point of instantiation is the point of instantiation of its enclosing templated entity, if any.

Otherwise, it immediately follows the namespace-scope declaration or definition that contains the expansion statement.