don't undefine unprefixed luatex primitives on rollback

base/ltdirchk.dtx

@@ -263,6 +263,10 @@
 % In current formats enable primitives with unprefixed names.
 % the \textsf{latexrelease} guards allow the primitives to be
 % defined with a |\luatex| prefix if older formats are specified.
+%
+% The unprefixed forms are \emph{not} undefined for improved
+% compatibility with external packages when rolling back
+% the format.
 %    \begin{macrocode}
 %</initex>
 %</dircheck>
@@ -280,25 +284,6 @@
 %<latexrelease>    "luatex",
 %<latexrelease>    tex.extraprimitives("core","omega", "aleph", "luatex")
 %<latexrelease>  )
-%<latexrelease>  local i
-%<latexrelease>  local t = { }
-%<latexrelease>  for _,i in pairs(tex.extraprimitives("luatex")) do
-%<latexrelease>    if not string.match(i,"^U") then
-%<latexrelease>      if not string.match(i, "^luatex") then
-%<latexrelease>        table.insert(t,i)
-%<latexrelease>      end
-%<latexrelease>    else
-%<latexrelease>      if string.match(i,"^Uchar$") then
-%<latexrelease>        table.insert(t,i)
-%<latexrelease>      end
-%<latexrelease>    end
-%<latexrelease>  end
-%<latexrelease>  for _,i in pairs(t) do
-%<latexrelease>    tex.print(
-%<latexrelease>      "\noexpand\\let\noexpand\\" .. i
-%<latexrelease>        .. "\noexpand\\undefined"
-%<latexrelease>    )
-%<latexrelease>  end
 %<latexrelease>}
 %<latexrelease>\EndIncludeInRelease
 %<latexrelease>\fi