1 files changed, 35 insertions, 2 deletions
diff --git a/macros/latex/contrib/l3packages/xparse.dtx b/macros/latex/contrib/l3packages/xparse.dtx
index fd4b615e15..f601bd9c5f 100644
--- a/macros/latex/contrib/l3packages/xparse.dtx
+++ b/macros/latex/contrib/l3packages/xparse.dtx
@@ -67,7 +67,7 @@
 %    }^^A
 % }
 %
-% \date{Released 2021-08-27}
+% \date{Released 2021-11-12}
 %
 % \maketitle
 %
@@ -1064,7 +1064,7 @@
 %    \end{macrocode}
 %
 %    \begin{macrocode}
-\ProvidesExplPackage{xparse}{2021-08-27}{}
+\ProvidesExplPackage{xparse}{2021-11-12}{}
   {L3 Experimental document command parser}
 %    \end{macrocode}
 %
@@ -1249,6 +1249,39 @@
 %    \end{macrocode}
 % \end{macro}
 %
+% \subsection{Copying a command and its internal structure}
+%
+% The apparatus for copying commands is almost entirely in |ltcmd.dtx|,
+% preloaded in the \LaTeXe{} kernel.  The missing parts, regarding
+% copying the deprecated argument types |G|, |l| and |u| boil down to
+% copying the expandable grabber for |u|.
+%
+% \begin{macro}{\@@_copy_grabber_u:w}
+%   An expandable |u|-type uses a dedicated grabber just like a
+%   |D|-type, except that both its delimiter tokens are omitted, so to
+%   copy that we just copy a |D|-type and leave the last two arguments
+%   empty:
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_copy_grabber_u:w #1 #2 #3
+  { \@@_copy_grabber_D:w {#1} {#2} {#3} { } { } }
+%    \end{macrocode}
+% \end{macro}
+%
+% \subsubsection{Showing the definition of a command}
+%
+% \begin{macro}{\c_@@_show_type_u_tl,\c_@@_show_type_G_tl}
+%   Same as for copying, only small bits are missing here.  Namely, two
+%   token lists that tell the \pkg{ltcmd} mechanism how to deal with the
+%   argument types defined here.  Both |G| and |u| are classified
+%   as~|3|: commands that take a default value.  That's not really true
+%   for~|u|, but it's a close enough approximation to get the output we
+%   want.
+%    \begin{macrocode}
+\tl_const:Nn \c_@@_show_type_u_tl { 3 }
+\tl_const:Nn \c_@@_show_type_G_tl { 3 }
+%    \end{macrocode}
+% \end{macro}
+%
 % \subsection{Grabbing arguments}
 %
 % \begin{macro}{\@@_grab_G:w}