LWG3818 Exposition-only concepts are not described in library intro

Fixes NB GB 074 (C++23 CD).

Author: burblebee

source/lib-intro.tex

@@ -478,13 +478,14 @@
 implementation-defined types\iref{type.descriptions},
 and member functions\iref{functions.within.classes}.
 
-\rSec3[expos.only.func]{Exposition-only functions}
+\rSec3[expos.only.entity]{Exposition-only entities, etc.}
 
 \pnum
-Several function templates
+Several entities and \grammarterm{typedef-name}{s}
 defined in \ref{\firstlibchapter} through \ref{\lastlibchapter} and \ref{depr}
 are only defined for the purpose of exposition.
-The declaration of such a function is followed by a comment ending in \expos.
+The declaration of such an entity or \grammarterm{typedef-name}
+is followed by a comment ending in \expos.
 
 \pnum
 The following are defined for exposition only
@@ -546,22 +547,6 @@
 \indextext{types!implementation-defined}%
 They are based on other types, but with added constraints.
 
-\rSec4[expos.only.types]{Exposition-only types}
-
-\pnum
-Several types defined in \ref{\firstlibchapter} through \ref{\lastlibchapter}
-and \ref{depr} are defined for the purpose of exposition.
-The declaration of such a type is followed by a comment ending in \expos.
-\begin{example}
-\begin{codeblock}
-namespace std {
-  extern "C" using @\placeholdernc{some-handler}@ = int(int, void*, double);  // \expos
-}
-\end{codeblock}
-The type placeholder \tcode{\placeholder{some-handler}} can now be used to specify a function
-that takes a callback parameter with C language linkage.
-\end{example}
-
 \rSec4[enumerated.types]{Enumerated types}
 
 \pnum

source/xrefdelta.tex

@@ -106,5 +106,9 @@
 % LWG3659 Consider ATOMIC_FLAG_INIT undeprecation
 \removedxref{depr.atomics.flag}
 
+% LWG3818 Exposition-only concepts are not described in library intro
+\movedxref{expos.only.func}{expos.only.entity}
+\removedxref{expos.only.types}
+
 % Deprecated features.
 %\deprxref{old.label}  (if moved to depr.old.label, otherwise use \movedxref)