CWG3171 Codify the strong ownership for modules

Fixes NB US 17-030, FR 003-031 (C++26 CD).
tkoeppe · Apr 12, 2026 · Apr 4, 2026 · Apr 4, 2026 · Apr 4, 2026 · Apr 4, 2026
commit 9b822e32e7d1ba9cb074b8cec8b55edbaede59a4
diff --git a/source/basic.tex b/source/basic.tex
@@ -3079,9 +3079,7 @@
 \item
 they both declare type aliases or namespace aliases that have the same underlying entity, or
 \item
-they both declare names with module linkage and are attached to the same module, or
-\item
-they both declare names with external linkage.
+they both declare names with module or external linkage and are attached to the same module.
 \end{itemize}
 \begin{note}
 There are other circumstances in which declarations declare
@@ -3098,9 +3096,11 @@
 \end{note}
 
 \pnum
-If two declarations of an entity are
-attached to different modules, the program is ill-formed;
-no diagnostic is required if neither is reachable from the other.
+\begin{note}
+If two declarations correspond but are
+attached to different modules, the program is ill-formed
+if one precedes the other\iref{basic.scope.scope}.
+\end{note}
 \begin{example}
 \begin{codeblocktu}{\tcode{"decls.h"}}
 int f();            // \#1, attached to the global module
@@ -3112,15 +3112,15 @@
 #include "decls.h"
 export module M;
 export using ::f;   // OK, does not declare an entity, exports \#1
-int g();            // error: matches \#2, but attached to \tcode{M}
+int g();            // error: corresponds to \#2, but attached to \tcode{M}
 export int h();     // \#3
 export int k();     // \#4
 \end{codeblocktu}
 
 \begin{codeblocktu}{Other translation unit}
 import M;
-static int h();     // error: matches \#3
-int k();            // error: matches \#4
+static int h();     // error: conflicts with \#3
+int k();            // error: conflicts with \#4
 \end{codeblocktu}
 \end{example}
 As a consequence of these rules,