[basic.lookup.general] (original) (raw)

6 Basics [basic]

6.5 Name lookup [basic.lookup]

6.5.1 General [basic.lookup.general]

Name lookup associates the use of a name with a set of declarations ([basic.def]) of that name.

Unless otherwise specified, the program is ill-formed if no declarations are found.

If the declarations found by name lookup all denote functions or function templates, the declarations are said to form an overload set.

Otherwise, if the declarations found by name lookup do not all denote the same entity,they are ambiguous and the program is ill-formed.

The access rules ([class.access]) are considered only once name lookup and function overload resolution (if applicable) have succeeded.

Only after name lookup, function overload resolution (if applicable) and access checking have succeeded are the semantic properties introduced by the declarations used in further processing.

A program point P is said to follow any declaration in the same translation unit whose locus ([basic.scope.pdecl]) is before P.

[Note 1:

The declaration might appear in a scope that does not contain P.

— _end note_]

A declaration X precedesa program point P in a translation unit Lif P follows X, X inhabits a class scope and is reachable from P, or else X appears in a translation unit D and

• P follows a module-import-declaration or module-declarationthat imports D (directly or indirectly), and
• X appears after the module-declaration in D (if any) and before the private-module-fragment in D (if any), and
• either X is exported or else D and L are part of the same module andX does not inhabit a namespace with internal linkage or declare a name with internal linkage.

[Note 3:

[Example 1:

Translation unit #1:export module Q;export int sq(int i) { return i*i; }

Translation unit #2:export module R;export import Q;

Translation unit #3:import R;int main() { return sq(9); } — _end example_]

— _end note_]

A single search in a scope Sfor a name N from a program point Pfinds all declarations that precede Pto which any name that is the same as N ([basic.pre]) is bound in S.

In certain contexts, only certain kinds of declarations are included.

After any such restriction, any declarations of classes or enumerations are discarded if any other declarations are found.

[Note 4:

A type (but not a typedef-name or template) is therefore hidden by any other entity in its scope.

— _end note_]

However, if a lookup is type-only, only declarations of types and templates whose specializations are types are considered; furthermore, if declarations of a typedef-name and of the type to which it refers are found, the declaration of the typedef-name is discarded instead of the type declaration.