Merge 2022-11 CWG Motion 11

P2615R1 Meaningful exports

Author: tkoeppe

source/basic.tex

@@ -48,7 +48,7 @@
 Every name is introduced by a \defn{declaration}, which is a
 \begin{itemize}
 \item
-\grammarterm{declaration},
+\grammarterm{name-declaration},
 \grammarterm{block-declaration}, or
 \grammarterm{member-declaration}\iref{dcl.pre,class.mem},
 \item
@@ -1753,10 +1753,6 @@
 if it precedes $P$ and inhabits either $S$ or
 the scope of a namespace nominated by a \grammarterm{using-directive}
 that is active in $S$ at $P$.
-\begin{note}
-A \grammarterm{using-directive} is exported if and only if
-it appears in a header unit.
-\end{note}
 
 \pnum
 An \term{unqualified search} in a scope $S$ from a program point $P$

source/declarations.tex

@@ -19,21 +19,31 @@
 
 \begin{bnf}
 \nontermdef{declaration}\br
+    name-declaration\br
+    special-declaration
+\end{bnf}
+
+\begin{bnf}
+\nontermdef{name-declaration}\br
     block-declaration\br
     nodeclspec-function-declaration\br
     function-definition\br
     template-declaration\br
     deduction-guide\br
-    explicit-instantiation\br
-    explicit-specialization\br
-    export-declaration\br
     linkage-specification\br
     namespace-definition\br
     empty-declaration\br
     attribute-declaration\br
     module-import-declaration
 \end{bnf}
 
+\begin{bnf}
+\nontermdef{special-declaration}\br
+    explicit-instantiation\br
+    explicit-specialization\br
+    export-declaration
+\end{bnf}
+
 \begin{bnf}
 \nontermdef{block-declaration}\br
     simple-declaration\br
@@ -8151,7 +8161,7 @@
 \begin{bnf}
 \nontermdef{linkage-specification}\br
     \keyword{extern} string-literal \terminal{\{} \opt{declaration-seq} \terminal{\}}\br
-    \keyword{extern} string-literal declaration
+    \keyword{extern} string-literal name-declaration
 \end{bnf}
 
 The \grammarterm{string-literal} indicates the required language linkage.
@@ -8185,9 +8195,6 @@
 \end{example}
 
 \pnum
-A \grammarterm{module-import-declaration}
-shall not be directly contained in
-a \grammarterm{linkage-specification}.
 A \grammarterm{module-import-declaration} appearing in
 a linkage specification with other than \Cpp{} language linkage
 is conditionally-supported with

source/modules.tex

@@ -196,7 +196,7 @@
 
 \begin{bnf}
 \nontermdef{export-declaration}\br
-    \keyword{export} declaration\br
+    \keyword{export} name-declaration\br
     \keyword{export} \terminal{\{} \opt{declaration-seq} \terminal{\}}\br
     export-keyword module-import-declaration
 \end{bnf}
@@ -209,10 +209,12 @@
 or a \grammarterm{private-module-fragment}.
 An \grammarterm{export-declaration}
 has the declarative effects of its
-\grammarterm{declaration},
+\grammarterm{name-declaration},
 \grammarterm{declaration-seq} (if any), or
 \grammarterm{module-import-declaration}.
-The \grammarterm{declaration} or \grammarterm{declaration-seq} of
+The \grammarterm{name-declaration} of an \grammarterm{export-declaration}
+shall not declare a partial specialization\iref{temp.decls.general}.
+The \grammarterm{declaration-seq} of
 an \grammarterm{export-declaration}
 shall not contain an \grammarterm{export-declaration} or
 \grammarterm{module-import-declaration}.
@@ -232,10 +234,7 @@
 \end{itemize}
 
 \pnum
-An exported declaration
-that is not a \grammarterm{module-import-declaration}
-shall declare at least one name.
-If the declaration is not within a header unit,
+If an exported declaration is not within a header unit,
 it shall not declare a name with internal linkage.
 
 \pnum
@@ -249,17 +248,14 @@
 #include "a.h"                  // error: declaration of \tcode{x} is not in the
                                 // purview of a module interface unit
 export module M;
-export namespace {}             // error: does not introduce any names
-export namespace {
-  int a1;                       // error: export of name with internal linkage
-}
+export namespace {}             // error: namespace has internal linkage
 namespace {
   export int a2;                // error: export of name with internal linkage
 }
 export static int b;            // error: b explicitly declared static
 export int f();                 // OK
 export namespace N { }          // OK
-export using namespace N;       // error: does not declare a name
+export using namespace N;       // OK
 \end{codeblocktu}
 \end{example}
 

source/templates.tex

@@ -6379,6 +6379,8 @@
 \end{example}
 
 \pnum
+The \grammarterm{declaration} in an \grammarterm{explicit-specialization}
+shall not be an \grammarterm{export-declaration}.
 An explicit specialization shall not use
 a \grammarterm{storage-class-specifier}\iref{dcl.stc}
 other than \keyword{thread_local}.