From Jason Turner

[namespace.udir]

C++17 → C++20 4.0 KB 46 lines
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Archived: C++17 | C++20
Markdown: C++17 | C++20
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  1. tmp/tmpswtok9nz/{from.md → to.md} +19 -20
tmp/tmpswtok9nz/{from.md → to.md} RENAMED
@@ -1,10 +1,10 @@
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- ### Using directive <a id="namespace.udir">[[namespace.udir]]</a>
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  ``` bnf
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  using-directive:
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- attribute-specifier-seqₒₚₜ 'using namespace' nested-name-specifierₒₚₜ namespace-name ';'
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  ```
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  A *using-directive* shall not appear in class scope, but may appear in
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  namespace scope or in block scope.
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@@ -15,12 +15,12 @@ only namespace names are considered, see 
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  The optional *attribute-specifier-seq* appertains to the
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  *using-directive*.
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  A *using-directive* specifies that the names in the nominated namespace
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  can be used in the scope in which the *using-directive* appears after
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- the *using-directive*. During unqualified name lookup (
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- [[basic.lookup.unqual]]), the names appear as if they were declared in
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  the nearest enclosing namespace which contains both the
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  *using-directive* and the nominated namespace.
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  [*Note 2*: In this context, “contains” means “contains directly or
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  indirectly”. — *end note*]
@@ -52,18 +52,18 @@ namespace A {
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  void f3() {
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  i = 5; // uses A::i
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  }
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  }
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  void f4() {
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- i = 5; // ill-formed; neither i is visible
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  }
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  ```
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  — *end example*]
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- For unqualified lookup ([[basic.lookup.unqual]]), the *using-directive*
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- is transitive: if a scope contains a *using-directive* that nominates a
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  second namespace that itself contains *using-directive*s, the effect is
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  as if the *using-directive*s from the second namespace also appeared in
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  the first.
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  [*Note 3*: For qualified lookup, see 
@@ -112,25 +112,24 @@ namespace B {
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  }
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  ```
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  — *end example*]
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- If a namespace is extended ([[namespace.def]]) after a
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- *using-directive* for that namespace is given, the additional members of
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- the extended namespace and the members of namespaces nominated by
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- *using-directive*s in the extending *namespace-definition* can be used
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- after the extending *namespace-definition*.
 
 
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  If name lookup finds a declaration for a name in two different
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  namespaces, and the declarations do not declare the same entity and do
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- not declare functions, the use of the name is ill-formed.
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-
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- [*Note 4*:
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-
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- In particular, the name of a variable, function or enumerator does not
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- hide the name of a class or enumeration declared in a different
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- namespace. For example,
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  ``` cpp
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  namespace A {
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  class X { };
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  extern "C" int g();
@@ -162,11 +161,11 @@ and the relationships among the namespaces implied by the
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  *using-directive*s do not cause preference to be given to any of the
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  declarations found by the search. — *end note*]
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  An ambiguity exists if the best match finds two functions with the same
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  signature, even if one is in a namespace reachable through
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- *using-directive*s in the namespace of the other.[^7]
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  [*Example 3*:
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  ``` cpp
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  namespace D {
 
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+ ### Using namespace directive <a id="namespace.udir">[[namespace.udir]]</a>
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  ``` bnf
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  using-directive:
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+ attribute-specifier-seqₒₚₜ using namespace nested-name-specifierₒₚₜ namespace-name ';'
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  ```
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  A *using-directive* shall not appear in class scope, but may appear in
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  namespace scope or in block scope.
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  The optional *attribute-specifier-seq* appertains to the
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  *using-directive*.
17
 
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  A *using-directive* specifies that the names in the nominated namespace
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  can be used in the scope in which the *using-directive* appears after
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+ the *using-directive*. During unqualified name lookup
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+ [[basic.lookup.unqual]], the names appear as if they were declared in
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  the nearest enclosing namespace which contains both the
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  *using-directive* and the nominated namespace.
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  [*Note 2*: In this context, “contains” means “contains directly or
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  indirectly”. — *end note*]
 
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  void f3() {
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  i = 5; // uses A::i
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  }
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  }
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  void f4() {
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+ i = 5; // error: neither i is visible
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  }
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  ```
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  — *end example*]
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+ For unqualified lookup [[basic.lookup.unqual]], the *using-directive* is
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+ transitive: if a scope contains a *using-directive* that nominates a
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  second namespace that itself contains *using-directive*s, the effect is
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  as if the *using-directive*s from the second namespace also appeared in
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  the first.
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  [*Note 3*: For qualified lookup, see 
 
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  }
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  ```
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  — *end example*]
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+ If a namespace is extended [[namespace.def]] after a *using-directive*
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+ for that namespace is given, the additional members of the extended
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+ namespace and the members of namespaces nominated by *using-directive*s
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+ in the extending *namespace-definition* can be used after the extending
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+ *namespace-definition*.
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+
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+ [*Note 4*:
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  If name lookup finds a declaration for a name in two different
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  namespaces, and the declarations do not declare the same entity and do
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+ not declare functions or function templates, the use of the name is
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+ ill-formed [[basic.lookup]]. In particular, the name of a variable,
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+ function or enumerator does not hide the name of a class or enumeration
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+ declared in a different namespace. For example,
 
 
 
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  ``` cpp
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  namespace A {
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  class X { };
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  extern "C" int g();
 
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  *using-directive*s do not cause preference to be given to any of the
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  declarations found by the search. — *end note*]
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  An ambiguity exists if the best match finds two functions with the same
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  signature, even if one is in a namespace reachable through
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+ *using-directive*s in the namespace of the other.[^11]
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  [*Example 3*:
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  ``` cpp
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  namespace D {