CWG2990 Exporting redeclarations of namespaces

Author: burblebee

source/modules.tex

@@ -312,14 +312,20 @@
 A redeclaration of an entity $X$
 is implicitly exported
 if $X$ was introduced by an exported declaration;
-otherwise it shall not be exported if it is attached to a named module.
+otherwise it shall not be exported unless it is a namespace.
 \begin{example}
 \begin{codeblock}
 export module M;
 struct S { int n; };
 typedef S S;
 export typedef S S;             // OK, does not redeclare an entity
 export struct S;                // error: exported declaration follows non-exported declaration
+namespace N {                   // external linkage, attached to global module, not exported
+  void f();
+}
+namespace N {                   // OK, exported namespace redeclaring non-exported namespace
+  export void g();
+}
 \end{codeblock}
 \end{example}