[namespace.udecl] A using-declarator does not introduce a name, but should

[t3nsor]

Full name of submitter: Brian Bi

Link to Mattermost thread: https://chat.isocpp.org/general/pl/3w7furqo4i8pfydse13d9tb4th

Issue description: A using-declarator that doesn't name a constructor should bind the unqualified-id in the scope where it appears. The note in [namespace.udecl]/2 suggests that the name is bound, but is not normative and doesn't specify the scope in which it's bound. Also, it is not clear whether there is actually a normative prohibition on something like using X::~X;.

Suggested resolution: Edit the grammar for [namespace.udecl] as shown:

using-declarator:
    typename_opt nested-name-specifier unqualified-id using-declarator-id

using-declarator-id:
    identifier
    operator-function-id
    conversion-function-id
    literal-operator-id

In [namespace.udecl]/1, replace both occurrences of "unqualified-id" with "using-declarator-id".

Edit [namespace.udecl]/2:

If the using-declarator names a constructor, it declares that the class inherits the named set of constructor declarations from the nominated base class. Otherwise, the using-declarator introduces its using-declarator-id. [Note 1: Otherwise, the unqualified-id in the using-declarator is bound to During name lookup, the using-declarator , which is replaced during name lookup with the declarations it names ([basic.lookup]). If such a declaration is of an enumeration, the names of its enumerators are not bound. For the keyword typename, see [temp.res]. — end note]

Strike Note 2 at the beginning of [namespace.udecl]/4:

[Note 2: Since destructors do not have names, a using-declaration cannot refer to a destructor for a base class. — end note] [...]

Strike [namespace.udecl]/5:

A using-declaration shall not name a template-id. [Example 3: ... ]