7 Expressions [expr]

7.5 Primary expressions [expr.prim]

7.5.5 Names [expr.prim.id]

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

qualified-id:
nested-name-specifier template

_{o p t}

unqualified-id

nested-name-specifier:
::
type-name ::
namespace-name ::
computed-type-specifier ::
nested-name-specifier identifier ::
nested-name-specifier template

_{o p t}

simple-template-id ::

The component names of a qualified-id are those of its nested-name-specifier and unqualified-id.

The component names of a nested-name-specifier are its identifier (if any) and those of its type-name, namespace-name, simple-template-id, and/or nested-name-specifier.

A nested-name-specifier is declarative if it is part of

(2.1)
a class-head-name,
(2.2)
an enum-head-name,
(2.3)
a qualified-id that is the id-expression of a declarator-id, or
(2.4)
a declarative nested-name-specifier.

A declarative nested-name-specifier shall not have a computed-type-specifier.

A declaration that uses a declarative nested-name-specifier shall be a friend declaration or inhabit a scope that contains the entity being redeclared or specialized.

The nested-name-specifier :: nominates the global namespace.

A nested-name-specifier with a computed-type-specifier nominates the type denoted by the computed-type-specifier, which shall be a class or enumeration type.

If a nested-name-specifier N is declarative and has a simple-template-id with a template argument list A that involves a template parameter, let T be the template nominated by N without A.

T shall be a class template.

(3.1)
If A is the template argument list ([temp.arg]) of the corresponding template-head H ([temp.mem]), N nominates the primary template of T; H shall be equivalent to the template-head of T ([temp.over.link]).
(3.2)
Otherwise, N nominates the partial specialization ([temp.spec.partial]) of T whose template argument list is equivalent to A ([temp.over.link]); the program is ill-formed if no such partial specialization exists.

Any other nested-name-specifier nominates the entity denoted by its type-name, namespace-name, identifier, or simple-template-id.

If the nested-name-specifier is not declarative, the entity shall not be a template.

A qualified-id shall not be of the form nested-name-specifier template

_{o p t}

~ computed-type-specifier nor of the form computed-type-specifier :: ~ type-name.

The result of a qualified-id Q is the entity it denotes ([basic.lookup.qual]).

If Q appears in the predicate of a contract assertion C ([basic.contract]) and the entity is

(6.1)
a variable declared outside of C of object type T,
(6.2)
a variable declared outside of C of type “reference to T”, or
(6.3)
a structured binding of type T whose corresponding variable is declared outside of C,

then the type of the expression is const T.

Otherwise, the type of the expression is the type of the result.

The result is an lvalue if the member is

(8.1)
a function other than a non-static member function,
(8.2)
a non-static member function if Q is the operand of a unary & operator,
(8.3)
a variable,
(8.4)
a structured binding ([dcl.struct.bind]), or
(8.5)
a data member,

and a prvalue otherwise.