Memoir update: Illegal parameter number in definition of \reserved@a

This is a bug in memoir.cls, which has code for emulating textcase.sty when the latter package is not installed.

However, code such as

\IfFileExists{<filename>}{<code>}{\def\foo#1{#1}}

doesn't work and, as far as I can tell, never has. The code should be

\IfFileExists{textcase.sty}{%
  \RequirePackage[overload]{textcase}\@tempswafalse
  }{\@tempswatrue}
\if@tempswa
% resort to the
%%%% Nearly a carbon copy from textcase.dtx by David Carlisle
\def\@uclcnotmath#1#2#3#4{\begingroup
      #1%
      \def\({$}\let\)\(% $ for emacs :-)
      \def\NoCaseChange##1{\noexpand\NoCaseChange{\noexpand##1}}%
      \@nonchangecase\label
      \@nonchangecase\ref
      \@nonchangecase\ensuremath
      \def\cite##1##{\toks@{\noexpand\cite##1}\@citex}%
      \def\@citex##1{\NoCaseChange{\the\toks@{##1}}}%
      \def\reserved@a##1##2{\let#2\reserved@a}%
      \expandafter\reserved@a\@uclclist\reserved@b{\reserved@b\@gobble}%
      \protected@edef\reserved@a{\endgroup
          \noexpand\@skipmath#3#4$\valign$}%
      \reserved@a}
\def\@nonchangecase#1{\def#1##1{\NoCaseChange{#1{##1}}}}
\let\NoCaseChange\@firstofone
\def\@skipmath#1#2$#3${%
  \@skip@nonchangecase#1#2\NoCaseChange\valign
  \ifx\valign#3%
  \else
    $#3$%
    \expandafter\@skipmath\expandafter#1%
  \fi}
\def\@skip@nonchangecase#1#2\NoCaseChange#3{%
  #1{#2}%
  \ifx\valign#3%
  \else
    #3%
    \expandafter\@skip@nonchangecase\expandafter#1%
  \fi}
\DeclareRobustCommand\MakeTextUppercase{%
  \@uclcnotmath{\def\i{I}\def\j{J}}{##1##2}\uppercase}
\protected@edef\MakeTextUppercase#1{\MakeTextUppercase{#1}}
\DeclareRobustCommand\MakeTextLowercase{%
  \@uclcnotmath{}{##2##1}\lowercase}
\protected@edef\MakeTextLowercase#1{\MakeTextLowercase{#1}}
%%%% End copy from textcase.dtx
\fi % end of \IfFileExists

so the code is not absorbed as an argument, but is only read if textcase.sty doesn't exist on the local system.

A fixed version of memoir (v3.7j) have been shipped to CTAN.

It now also includes a warning if you do not have the textcase package on your system.