7 Expressions [expr]

7.5 Primary expressions [expr.prim]

7.5.4 Names [expr.prim.id]

7.5.4.2 Qualified names [expr.prim.id.qual]

qualified-id:
	nested-name-specifier template unqualified-id

nested-name-specifier:
	::
	type-name ::
	namespace-name ::
	decltype-specifier ::
	nested-name-specifier identifier ::
	nested-name-specifier template simple-template-id ::
1
#
The type denoted by a decltype-specifier in a nested-name-specifier shall be a class or enumeration type.
2
#
A nested-name-specifier that denotes a class, optionally followed by the keyword template ([temp.names]), and then followed by the name of a member of either that class ([class.mem]) or one of its base classes, is a qualified-id; [class.qual] describes name lookup for class members that appear in qualified-ids.
The result is the member.
The type of the result is the type of the member.
The result is an lvalue if the member is a static member function or a data member and a prvalue otherwise.
[ Note
:
A class member can be referred to using a qualified-id at any point in its potential scope ([basic.scope.class]).
— end note
 ]
Where type-name ​::​~ type-name is used, the two type-names shall refer to the same type (ignoring cv-qualifications); this notation denotes the destructor of the type so named ([expr.prim.id.dtor]).
The unqualified-id in a qualified-id shall not be of the form ~decltype-specifier.
3
#
The nested-name-specifier ​::​ names the global namespace.
A nested-name-specifier that names a namespace, optionally followed by the keyword template ([temp.names]), and then followed by the name of a member of that namespace (or the name of a member of a namespace made visible by a using-directive), is a qualified-id; [namespace.qual] describes name lookup for namespace members that appear in qualified-ids.
The result is the member.
The type of the result is the type of the member.
The result is an lvalue if the member is a function, a variable, or a structured binding ([dcl.struct.bind]) and a prvalue otherwise.
4
#
A nested-name-specifier that denotes an enumeration, followed by the name of an enumerator of that enumeration, is a qualified-id that refers to the enumerator.
The result is the enumerator.
The type of the result is the type of the enumeration.
The result is a prvalue.
5
#
In a qualified-id, if the unqualified-id is a conversion-function-id, its conversion-type-id is first looked up in the class denoted by the nested-name-specifier of the qualified-id and the name, if found, is used.
Otherwise, it is looked up in the context in which the entire qualified-id occurs.
In each of these lookups, only names that denote types or templates whose specializations are types are considered.