tmp/tmp2nce8dui/{from.md → to.md}
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| 1 |
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### General <a id="basic.lookup.general">[[basic.lookup.general]]</a>
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The name lookup rules apply uniformly to all names (including
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*typedef-name*s [[dcl.typedef]], *namespace-name*s [[basic.namespace]],
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and *class-name*s [[class.name]]) wherever the grammar allows such names
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in the context discussed by a particular rule. Name lookup associates
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the use of a name with a set of declarations [[basic.def]] of that name.
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Unless otherwise specified, the program is ill-formed if no declarations
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are found. If the declarations found by name lookup all denote functions
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or function templates, the declarations are said to form an *overload
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set*. Otherwise, if the declarations found by name lookup do not all
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denote the same entity, they are *ambiguous* and the program is
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ill-formed. Overload resolution [[over.match]], [[over.over]] takes
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place after name lookup has succeeded. The access rules [[class.access]]
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are considered only once name lookup and function overload resolution
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(if applicable) have succeeded. Only after name lookup, function
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overload resolution (if applicable) and access checking have succeeded
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are the semantic properties introduced by the declarations used in
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further processing.
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A program point P is said to follow any declaration in the same
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translation unit whose locus [[basic.scope.pdecl]] is before P.
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[*Note 1*: The declaration might appear in a scope that does not
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contain P. — *end note*]
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A declaration X *precedes* a program point P in a translation unit L if
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P follows X, X inhabits a class scope and is reachable from P, or else X
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appears in a translation unit D and
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- P follows a *module-import-declaration* or *module-declaration* that
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imports D (directly or indirectly), and
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- X appears after the *module-declaration* in D (if any) and before the
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*private-module-fragment* in D (if any), and
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- either X is exported or else D and L are part of the same module and X
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does not inhabit a namespace with internal linkage or declare a name
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with internal linkage. \[*Note 2*: Names declared by a
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*using-declaration* have no linkage. — *end note*]
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[*Note 3*:
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A *module-import-declaration* imports both the named translation unit(s)
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and any modules named by exported *module-import-declaration*s within
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them, recursively.
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[*Example 1*:
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Translation unit #1
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``` cpp
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export module Q;
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export int sq(int i) { return i*i; }
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```
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Translation unit #2
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``` cpp
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export module R;
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export import Q;
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```
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Translation unit #3
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``` cpp
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import R;
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int main() { return sq(9); } // OK, sq from module Q
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```
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— *end example*]
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— *end note*]
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A *single search* in a scope S for a name N from a program point P finds
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all declarations that precede P to which any name that is the same as N
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[[basic.pre]] is bound in S. If any such declaration is a
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*using-declarator* whose terminal name [[expr.prim.id.unqual]] is not
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dependent [[temp.dep.type]], it is replaced by the declarations named by
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the *using-declarator* [[namespace.udecl]].
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In certain contexts, only certain kinds of declarations are included.
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After any such restriction, any declarations of classes or enumerations
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are discarded if any other declarations are found.
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[*Note 4*: A type (but not a *typedef-name* or template) is therefore
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hidden by any other entity in its scope. — *end note*]
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However, if a lookup is *type-only*, only declarations of types and
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templates whose specializations are types are considered; furthermore,
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if declarations of a *typedef-name* and of the type to which it refers
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are found, the declaration of the *typedef-name* is discarded instead of
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the type declaration.
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