1 files changed, 185 insertions, 92 deletions

diff --git a/Master/texmf-dist/source/latex/l3kernel/l3skip.dtx b/Master/texmf-dist/source/latex/l3kernel/l3skip.dtx
index bc7f26ed868..a20a48ccc66 100644
--- a/Master/texmf-dist/source/latex/l3kernel/l3skip.dtx
+++ b/Master/texmf-dist/source/latex/l3kernel/l3skip.dtx
@@ -8,7 +8,7 @@
 % license or (at your option) any later version.  The latest version
 % of this license is in the file
 %
-%    http://www.latex-project.org/lppl.txt
+%    https://www.latex-project.org/lppl.txt
 %
 % This file is part of the "l3kernel bundle" (The Work in LPPL)
 % and all files in that bundle must be distributed together.
@@ -22,7 +22,7 @@
 % for those people who are interested.
 %
 %<*driver>
-\documentclass[full]{l3doc}
+\documentclass[full,kernel]{l3doc}
 \begin{document}
   \DocInput{\jobname.dtx}
 \end{document}
@@ -42,7 +42,7 @@
 %    }^^A
 % }
 %
-% \date{Released 2017/11/14}
+% \date{Released 2017/12/05}
 %
 % \maketitle
 %
@@ -1011,6 +1011,16 @@
 %   \end{texnote}
 % \end{function}
 %
+% \begin{function}[EXP]{\__dim_eval:n}
+%   \begin{syntax}
+%     \cs{__dim_eval:n} \Arg{dimexpr}
+%   \end{syntax}
+%   By default this expands to \cs{__dim_eval:w} \meta{dimexpr}
+%   \cs{__dim_eval_end:} but when debugging is enabled this expands to a
+%   more complicated construction that evaluates \meta{dimexpr} with
+%   parentheses and within a brace group to detect early termination.
+% \end{function}
+%
 % \end{documentation}
 %
 % \begin{implementation}
@@ -1058,12 +1068,17 @@
 %
 % \begin{macro}{\dim_const:Nn, \dim_const:cn}
 %   Contrarily to integer constants, we cannot avoid using a register,
-%   even for constants.
-%    \begin{macrocode}
-\cs_new_protected:Npn \dim_const:Nn #1
+%   even for constants.  We cannot use \cs{dim_gset:Nn} because
+%   debugging code would complain that the constant is not a global
+%   variable.  Since \cs{dim_const:Nn} does not need to be fast, use
+%   \cs{dim_eval:n} to avoid needing a debugging patch that wraps the
+%   expression in checking code.
+%    \begin{macrocode}
+\__debug_patch:nnNNpn { \__debug_chk_var_scope:NN c #1 } { }
+\cs_new_protected:Npn \dim_const:Nn #1#2
   {
     \dim_new:N #1
-    \dim_gset:Nn #1
+    \tex_global:D #1 ~ \dim_eval:n {#2} \scan_stop:
   }
 \cs_generate_variant:Nn \dim_const:Nn { c }
 %    \end{macrocode}
@@ -1071,10 +1086,15 @@
 %
 % \begin{macro}{\dim_zero:N, \dim_zero:c}
 % \begin{macro}{\dim_gzero:N, \dim_gzero:c}
-%   Reset the register to zero.
-%    \begin{macrocode}
-\cs_new_protected:Npn \dim_zero:N #1 { #1 \c_zero_dim }
-\cs_new_protected:Npn \dim_gzero:N { \tex_global:D \dim_zero:N }
+%   Reset the register to zero.  Using \cs{c_zero_skip} deals with the
+%   case where the variable passed is incorrectly a skip (for example a
+%   \LaTeXe{} length).
+%    \begin{macrocode}
+\__debug_patch:nnNNpn { \__debug_chk_var_local:N #1 } { }
+\cs_new_protected:Npn \dim_zero:N #1 { #1 \c_zero_skip }
+\__debug_patch:nnNNpn { \__debug_chk_var_global:N #1 } { }
+\cs_new_protected:Npn \dim_gzero:N #1
+  { \tex_global:D #1 \c_zero_skip }
 \cs_generate_variant:Nn \dim_zero:N  { c }
 \cs_generate_variant:Nn \dim_gzero:N { c }
 %    \end{macrocode}
@@ -1106,15 +1126,36 @@
 %
 % \subsection{Setting \texttt{dim} variables}
 %
+% Several functions here have a signature |:Nn| and are such that when
+% debugging, the first argument should be checked to be a local/global
+% variable and the second should be wrapped in code for an expression.
+% The temporary function \cs{@@_tmp:w} finds the name |#3| of the
+% function being redefined and writes the appropriate patch.
+%    \begin{macrocode}
+\cs_set_protected:Npn \@@_tmp:w #1#2#3
+  {
+    \__debug_patch_args:nnnNNpn
+      { #1 ##1 }
+      { }
+      { {##1} { \__debug_chk_expr:nNnN {##2} \@@_eval:w { } #3 } }
+    #2 #3
+  }
+%    \end{macrocode}
+%
 % \begin{macro}{\dim_set:Nn, \dim_set:cn}
 % \begin{macro}{\dim_gset:Nn, \dim_gset:cn}
-%   Setting dimensions is easy enough.
+%   Setting dimensions is easy enough but when debugging we want both to
+%   check that the variable is correctly local/global and to wrap the
+%   expression in some code.  The \cs{scan_stop:} deals with the case
+%   where the variable passed is a skip (for example a \LaTeXe{}
+%   length).
 %    \begin{macrocode}
-\__debug_patch_args:nNNpn
-  { {#1} { \__debug_chk_expr:nNnN {#2} \@@_eval:w { } \dim_set:Nn } }
+\@@_tmp:w \__debug_chk_var_local:N
 \cs_new_protected:Npn \dim_set:Nn #1#2
-  { #1 ~ \@@_eval:w #2 \@@_eval_end: }
-\cs_new_protected:Npn \dim_gset:Nn { \tex_global:D \dim_set:Nn }
+  { #1 ~ \@@_eval:w #2 \@@_eval_end: \scan_stop: }
+\@@_tmp:w \__debug_chk_var_global:N
+\cs_new_protected:Npn \dim_gset:Nn #1#2
+  { \tex_global:D #1 ~ \@@_eval:w #2 \@@_eval_end: \scan_stop: }
 \cs_generate_variant:Nn \dim_set:Nn  { c }
 \cs_generate_variant:Nn \dim_gset:Nn { c }
 %    \end{macrocode}
@@ -1124,12 +1165,17 @@
 % \begin{macro}{\dim_set_eq:NN, \dim_set_eq:cN, \dim_set_eq:Nc, \dim_set_eq:cc}
 % \begin{macro}
 %   {\dim_gset_eq:NN, \dim_gset_eq:cN, \dim_gset_eq:Nc, \dim_gset_eq:cc}
-%   All straightforward.
+%   All straightforward, with a \cs{scan_stop:} to deal with the case
+%   where |#1| is (incorrectly) a skip.
 %    \begin{macrocode}
-\cs_new_protected:Npn \dim_set_eq:NN #1#2 { #1 = #2 }
+\__debug_patch:nnNNpn { \__debug_chk_var_local:N #1 } { }
+\cs_new_protected:Npn \dim_set_eq:NN #1#2
+  { #1 = #2 \scan_stop: }
 \cs_generate_variant:Nn \dim_set_eq:NN {       c }
 \cs_generate_variant:Nn \dim_set_eq:NN { Nc , cc }
-\cs_new_protected:Npn \dim_gset_eq:NN #1#2 { \tex_global:D #1 = #2 }
+\__debug_patch:nnNNpn { \__debug_chk_var_global:N #1 } { }
+\cs_new_protected:Npn \dim_gset_eq:NN #1#2
+  { \tex_global:D #1 = #2 \scan_stop: }
 \cs_generate_variant:Nn \dim_gset_eq:NN {       c }
 \cs_generate_variant:Nn \dim_gset_eq:NN { Nc , cc }
 %    \end{macrocode}
@@ -1141,19 +1187,26 @@
 % \begin{macro}{\dim_sub:Nn, \dim_sub:cn}
 % \begin{macro}{\dim_gsub:Nn, \dim_gsub:cn}
 %   Using |by| here deals with the (incorrect) case |\dimen123|.
+%   Using \cs{scan_stop:} deals with skip variables.  Since
+%   debugging checks that the variable is correctly local/global, the
+%   global versions cannot be defined as \cs{tex_global:D} followed by
+%   the local versions.  The debugging code is inserted by
+%   \cs{@@_tmp:w}.
 %    \begin{macrocode}
-\__debug_patch_args:nNNpn
-  { {#1} { \__debug_chk_expr:nNnN {#2} \@@_eval:w { } \dim_add:Nn } }
+\@@_tmp:w \__debug_chk_var_local:N
 \cs_new_protected:Npn \dim_add:Nn #1#2
-  { \tex_advance:D #1 by \@@_eval:w #2 \@@_eval_end: }
-\cs_new_protected:Npn \dim_gadd:Nn { \tex_global:D \dim_add:Nn }
+  { \tex_advance:D #1 by \@@_eval:w #2 \@@_eval_end: \scan_stop: }
+\@@_tmp:w \__debug_chk_var_global:N
+\cs_new_protected:Npn \dim_gadd:Nn #1#2
+  { \tex_global:D \tex_advance:D #1 by \@@_eval:w #2 \@@_eval_end: \scan_stop: }
 \cs_generate_variant:Nn \dim_add:Nn  { c }
 \cs_generate_variant:Nn \dim_gadd:Nn { c }
-\__debug_patch_args:nNNpn
-  { {#1} { \__debug_chk_expr:nNnN {#2} \@@_eval:w { } \dim_sub:Nn } }
+\@@_tmp:w \__debug_chk_var_local:N
 \cs_new_protected:Npn \dim_sub:Nn #1#2
-  { \tex_advance:D #1 by - \@@_eval:w #2 \@@_eval_end: }
-\cs_new_protected:Npn \dim_gsub:Nn { \tex_global:D \dim_sub:Nn }
+  { \tex_advance:D #1 by - \@@_eval:w #2 \@@_eval_end: \scan_stop: }
+\@@_tmp:w \__debug_chk_var_global:N
+\cs_new_protected:Npn \dim_gsub:Nn #1#2
+  { \tex_global:D \tex_advance:D #1 by - \@@_eval:w #2 \@@_eval_end: \scan_stop: }
 \cs_generate_variant:Nn \dim_sub:Nn  { c }
 \cs_generate_variant:Nn \dim_gsub:Nn { c }
 %    \end{macrocode}
@@ -1165,11 +1218,11 @@
 % \subsection{Utilities for dimension calculations}
 %
 % \begin{macro}[EXP]{\dim_abs:n}
-% \begin{macro}[aux, EXP]{\@@_abs:N}
+% \begin{macro}[EXP]{\@@_abs:N}
 % \UnitTested
 % \begin{macro}[EXP]{\dim_max:nn}
 % \begin{macro}[EXP]{\dim_min:nn}
-% \begin{macro}[aux, EXP]{\@@_maxmin:wwN}
+% \begin{macro}[EXP]{\@@_maxmin:wwN}
 % \UnitTested
 % \UnitTested
 %   Functions for $\min$, $\max$, and absolute value with only one evaluation.
@@ -1226,7 +1279,7 @@
 % \end{macro}
 %
 % \begin{macro}{\dim_ratio:nn}
-% \begin{macro}[aux]{\@@_ratio:n}
+% \begin{macro}{\@@_ratio:n}
 %   With dimension expressions, something like |10 pt * ( 5 pt / 10 pt )| does
 %   not work. Instead, the ratio part needs to be converted to an integer
 %   expression. Using \cs{__int_value:w} forces everything into |sp|, avoiding
@@ -1260,8 +1313,8 @@
 % \end{macro}
 %
 % \begin{macro}[pTF, EXP]{\dim_compare:n}
-% \begin{macro}[aux, EXP]{\@@_compare:w, \@@_compare:wNN}
-% \begin{macro}[aux, EXP]
+% \begin{macro}[EXP]{\@@_compare:w, \@@_compare:wNN}
+% \begin{macro}[EXP]
 %   {
 %     \@@_compare_=:w,
 %     \@@_compare_!:w,
@@ -1290,9 +1343,7 @@
       \@@_compare:wNN #1 ? { = \@@_compare_end:w \else: } \q_stop
   }
 \exp_args:Nno \use:nn
-  { \cs_new:Npn \@@_compare:wNN #1 }
-  { \tl_to_str:n {pt} }
-  #2#3
+  { \cs_new:Npn \@@_compare:wNN #1 } { \tl_to_str:n {pt} #2#3 }
   {
       \if_meaning:w = #3
         \use:c { @@_compare_#2:w }
@@ -1321,8 +1372,8 @@
 % \end{macro}
 %
 % \begin{macro}[EXP, noTF]{\dim_case:nn}
-% \begin{macro}[aux]{\@@_case:nnTF}
-% \begin{macro}[aux]{\@@_case:nw, \@@_case_end:nw}
+% \begin{macro}{\@@_case:nnTF}
+% \begin{macro}{\@@_case:nw, \@@_case_end:nw}
 %   For dimension cases, the first task to fully expand the check
 %   condition. The over all idea is then much the same as for
 %   \cs[index=str_case:nnTF]{str_case:nn(TF)} as described in \pkg{l3basics}.
@@ -1457,6 +1508,18 @@
 %    \end{macrocode}
 % \end{macro}
 %
+% \begin{macro}{\@@_eval:n}
+%   Evaluating a dimension expression expandably.  This is for use in
+%   other modules, to avoid having to patch many commands.  The only
+%   difference with \cs{dim_eval:n} is the lack of \cs{dim_use:N}, to
+%   produce an internal dimension rather than expand it into characters.
+%    \begin{macrocode}
+\__debug_patch_args:nNNpn
+  { { \__debug_chk_expr:nNnN {#1} \@@_eval:w { } \@@_eval:n } }
+\cs_new:Npn \@@_eval:n #1 { \@@_eval:w #1 \@@_eval_end: }
+%    \end{macrocode}
+% \end{macro}
+%
 % \begin{macro}{\dim_use:N, \dim_use:c}
 %   Accessing a \meta{dim}.
 %    \begin{macrocode}
@@ -1470,7 +1533,7 @@
 % \end{macro}
 %
 % \begin{macro}[EXP]{\dim_to_decimal:n}
-% \begin{macro}[EXP, aux]{\@@_to_decimal:w}
+% \begin{macro}[EXP]{\@@_to_decimal:w}
 %   A function which comes up often enough to deserve a place in the
 %   kernel.  Evaluate the dimension expression~|#1| then remove the
 %   trailing \texttt{pt}.  When debugging is enabled, the argument is
@@ -1556,7 +1619,7 @@
 %   dimension expressions: this gives a more unified output.
 %    \begin{macrocode}
 \cs_new_protected:Npn \dim_show:n
-  { \__msg_show_wrap:Nn \dim_eval:n }
+  { \msg_show_eval:Nn \dim_eval:n }
 %    \end{macrocode}
 %  \end{macro}
 %
@@ -1566,7 +1629,7 @@
 \cs_new_eq:NN \dim_log:N \__kernel_register_log:N
 \cs_new_eq:NN \dim_log:c \__kernel_register_log:c
 \cs_new_protected:Npn \dim_log:n
-  { \__msg_log_next: \dim_show:n }
+  { \msg_log_eval:Nn \dim_eval:n }
 %    \end{macrocode}
 % \end{macro}
 %
@@ -1613,12 +1676,14 @@
 %
 % \begin{macro}{\skip_const:Nn, \skip_const:cn}
 %   Contrarily to integer constants, we cannot avoid using a register,
-%   even for constants.
+%   even for constants.  See \cs{dim_const:Nn} for why we cannot use
+%   \cs{skip_gset:Nn}.
 %    \begin{macrocode}
-\cs_new_protected:Npn \skip_const:Nn #1
+\__debug_patch:nnNNpn { \__debug_chk_var_scope:NN c #1 } { }
+\cs_new_protected:Npn \skip_const:Nn #1#2
   {
     \skip_new:N #1
-    \skip_gset:Nn #1
+    \tex_global:D #1 ~ \skip_eval:n {#2} \scan_stop:
   }
 \cs_generate_variant:Nn \skip_const:Nn { c }
 %    \end{macrocode}
@@ -1628,8 +1693,10 @@
 % \begin{macro}{\skip_gzero:N, \skip_gzero:c}
 %   Reset the register to zero.
 %    \begin{macrocode}
+\__debug_patch:nnNNpn { \__debug_chk_var_local:N #1 } { }
 \cs_new_protected:Npn \skip_zero:N #1 { #1 \c_zero_skip }
-\cs_new_protected:Npn \skip_gzero:N { \tex_global:D \skip_zero:N }
+\__debug_patch:nnNNpn { \__debug_chk_var_global:N #1 } { }
+\cs_new_protected:Npn \skip_gzero:N #1 { \tex_global:D #1 \c_zero_skip }
 \cs_generate_variant:Nn \skip_zero:N  { c }
 \cs_generate_variant:Nn \skip_gzero:N { c }
 %    \end{macrocode}
@@ -1661,15 +1728,31 @@
 %
 % \subsection{Setting \texttt{skip} variables}
 %
+% Much as for \texttt{dim} variables, \cs{@@_tmp:w} prepares a patch
+% for |:Nn| function definitions in which the first argument should be
+% checked to be a local/global variable and the second should be wrapped
+% in code for an expression.
+%    \begin{macrocode}
+\cs_set_protected:Npn \@@_tmp:w #1#2#3
+  {
+    \__debug_patch_args:nnnNNpn
+      { #1 ##1 }
+      { }
+      { {##1} { \__debug_chk_expr:nNnN {##2} \etex_glueexpr:D { } #3 } }
+    #2 #3
+  }
+%    \end{macrocode}
+%
 % \begin{macro}{\skip_set:Nn, \skip_set:cn}
 % \begin{macro}{\skip_gset:Nn, \skip_gset:cn}
 %   Much the same as for dimensions.
 %    \begin{macrocode}
-\__debug_patch_args:nNNpn
-  { {#1} { \__debug_chk_expr:nNnN {#2} \etex_glueexpr:D { } \skip_set:Nn } }
+\@@_tmp:w \__debug_chk_var_local:N
 \cs_new_protected:Npn \skip_set:Nn #1#2
   { #1 ~ \etex_glueexpr:D #2 \scan_stop: }
-\cs_new_protected:Npn \skip_gset:Nn { \tex_global:D \skip_set:Nn }
+\@@_tmp:w \__debug_chk_var_global:N
+\cs_new_protected:Npn \skip_gset:Nn #1#2
+  { \tex_global:D #1 ~ \etex_glueexpr:D #2 \scan_stop: }
 \cs_generate_variant:Nn \skip_set:Nn  { c }
 \cs_generate_variant:Nn \skip_gset:Nn { c }
 %    \end{macrocode}
@@ -1698,18 +1781,20 @@
 % \begin{macro}{\skip_gsub:Nn, \skip_gsub:cn}
 %   Using |by| here deals with the (incorrect) case |\skip123|.
 %    \begin{macrocode}
-\__debug_patch_args:nNNpn
-  { {#1} { \__debug_chk_expr:nNnN {#2} \etex_glueexpr:D { } \skip_add:Nn } }
+\@@_tmp:w \__debug_chk_var_local:N
 \cs_new_protected:Npn \skip_add:Nn #1#2
   { \tex_advance:D #1 by \etex_glueexpr:D #2 \scan_stop: }
-\cs_new_protected:Npn \skip_gadd:Nn { \tex_global:D \skip_add:Nn }
+\@@_tmp:w \__debug_chk_var_global:N
+\cs_new_protected:Npn \skip_gadd:Nn #1#2
+  { \tex_global:D \tex_advance:D #1 by \etex_glueexpr:D #2 \scan_stop: }
 \cs_generate_variant:Nn \skip_add:Nn  { c }
 \cs_generate_variant:Nn \skip_gadd:Nn { c }
-\__debug_patch_args:nNNpn
-  { {#1} { \__debug_chk_expr:nNnN {#2} \etex_glueexpr:D { } \skip_sub:Nn } }
+\@@_tmp:w \__debug_chk_var_local:N
 \cs_new_protected:Npn \skip_sub:Nn #1#2
   { \tex_advance:D #1 by - \etex_glueexpr:D #2 \scan_stop: }
-\cs_new_protected:Npn \skip_gsub:Nn { \tex_global:D \skip_sub:Nn }
+\@@_tmp:w \__debug_chk_var_global:N
+\cs_new_protected:Npn \skip_gsub:Nn #1#2
+  { \tex_global:D \tex_advance:D #1 by - \etex_glueexpr:D #2 \scan_stop: }
 \cs_generate_variant:Nn \skip_sub:Nn  { c }
 \cs_generate_variant:Nn \skip_gsub:Nn { c }
 %    \end{macrocode}
@@ -1738,7 +1823,7 @@
 % \end{macro}
 %
 % \begin{macro}[EXP,pTF]{\skip_if_finite:n}
-% \begin{macro}[EXP,aux]{\__skip_if_finite:wwNw}
+% \begin{macro}[EXP]{\__skip_if_finite:wwNw}
 %   With \eTeX{}, we have an easy access to the order of infinities of
 %   the stretch and shrink components of a skip.  However, to access
 %   both, we either need to evaluate the expression twice, or evaluate
@@ -1747,7 +1832,7 @@
 %   it is quicker to make it search for the string \texttt{fil} which
 %   characterizes infinite glue.
 %    \begin{macrocode}
-\cs_set_protected:Npn \__cs_tmp:w #1
+\cs_set_protected:Npn \@@_tmp:w #1
   {
     \__debug_patch_conditional_args:nNNpnn
       {
@@ -1764,7 +1849,7 @@
       }
     \cs_new:Npn \__skip_if_finite:wwNw ##1 #1 ##2 ; ##3 ##4 \q_stop {##3}
   }
-\exp_args:No \__cs_tmp:w { \tl_to_str:n { fil } }
+\exp_args:No \@@_tmp:w { \tl_to_str:n { fil } }
 %    \end{macrocode}
 % \end{macro}
 % \end{macro}
@@ -1827,7 +1912,7 @@
 %   skip expressions: this gives a more unified output.
 %    \begin{macrocode}
 \cs_new_protected:Npn \skip_show:n
-  { \__msg_show_wrap:Nn \skip_eval:n }
+  { \msg_show_eval:Nn \skip_eval:n }
 %    \end{macrocode}
 % \end{macro}
 %
@@ -1837,7 +1922,7 @@
 \cs_new_eq:NN \skip_log:N \__kernel_register_log:N
 \cs_new_eq:NN \skip_log:c \__kernel_register_log:c
 \cs_new_protected:Npn \skip_log:n
-  { \__msg_log_next: \skip_show:n }
+  { \msg_log_eval:Nn \skip_eval:n }
 %    \end{macrocode}
 % \end{macro}
 %
@@ -1884,13 +1969,13 @@
 % \end{macro}
 %
 % \begin{macro}{\muskip_const:Nn, \muskip_const:cn}
-%   Contrarily to integer constants, we cannot avoid using a register,
-%   even for constants.
+%   See \cs{skip_const:Nn}.
 %    \begin{macrocode}
-\cs_new_protected:Npn \muskip_const:Nn #1
+\__debug_patch:nnNNpn { \__debug_chk_var_scope:NN c #1 } { }
+\cs_new_protected:Npn \muskip_const:Nn #1#2
   {
     \muskip_new:N #1
-    \muskip_gset:Nn #1
+    \tex_global:D #1 ~ \muskip_eval:n {#2} \scan_stop:
   }
 \cs_generate_variant:Nn \muskip_const:Nn { c }
 %    \end{macrocode}
@@ -1900,9 +1985,12 @@
 % \begin{macro}{\muskip_gzero:N, \muskip_gzero:c}
 %   Reset the register to zero.
 %    \begin{macrocode}
+\__debug_patch:nnNNpn { \__debug_chk_var_local:N #1 } { }
 \cs_new_protected:Npn \muskip_zero:N #1
   { #1 \c_zero_muskip }
-\cs_new_protected:Npn \muskip_gzero:N { \tex_global:D \muskip_zero:N }
+\__debug_patch:nnNNpn { \__debug_chk_var_global:N #1 } { }
+\cs_new_protected:Npn \muskip_gzero:N #1
+  { \tex_global:D #1 \c_zero_muskip }
 \cs_generate_variant:Nn \muskip_zero:N  { c }
 \cs_generate_variant:Nn \muskip_gzero:N { c }
 %    \end{macrocode}
@@ -1937,21 +2025,34 @@
 %
 % \subsection{Setting \texttt{muskip} variables}
 %
+% See \texttt{skip} case.
+%    \begin{macrocode}
+\cs_set_protected:Npn \@@_tmp:w #1#2#3
+  {
+    \__debug_patch_args:nnnNNpn
+      { #1 ##1 }
+      { }
+      {
+        {##1}
+        {
+          \__debug_chk_expr:nNnN {##2}
+            \etex_muexpr:D { \etex_mutoglue:D } #3
+        }
+      }
+    #2 #3
+  }
+%    \end{macrocode}
+%
 % \begin{macro}{\muskip_set:Nn, \muskip_set:cn}
 % \begin{macro}{\muskip_gset:Nn, \muskip_gset:cn}
 %   This should be pretty familiar.
 %    \begin{macrocode}
-\__debug_patch_args:nNNpn
-  {
-    {#1}
-    {
-      \__debug_chk_expr:nNnN {#2} \etex_muexpr:D
-        { \etex_mutoglue:D } \muskip_set:Nn
-    }
-  }
+\@@_tmp:w \__debug_chk_var_local:N
 \cs_new_protected:Npn \muskip_set:Nn #1#2
   { #1 ~ \etex_muexpr:D #2 \scan_stop: }
-\cs_new_protected:Npn \muskip_gset:Nn { \tex_global:D \muskip_set:Nn }
+\@@_tmp:w \__debug_chk_var_global:N
+\cs_new_protected:Npn \muskip_gset:Nn #1#2
+  { \tex_global:D #1 ~ \etex_muexpr:D #2 \scan_stop: }
 \cs_generate_variant:Nn \muskip_set:Nn  { c }
 \cs_generate_variant:Nn \muskip_gset:Nn { c }
 %    \end{macrocode}
@@ -1970,9 +2071,11 @@
 %   }
 %   All straightforward.
 %    \begin{macrocode}
+\__debug_patch:nnNNpn { \__debug_chk_var_local:N #1 } { }
 \cs_new_protected:Npn \muskip_set_eq:NN #1#2 { #1 = #2 }
 \cs_generate_variant:Nn \muskip_set_eq:NN {       c }
 \cs_generate_variant:Nn \muskip_set_eq:NN { Nc , cc }
+\__debug_patch:nnNNpn { \__debug_chk_var_global:N #1 } { }
 \cs_new_protected:Npn \muskip_gset_eq:NN #1#2 { \tex_global:D #1 = #2 }
 \cs_generate_variant:Nn \muskip_gset_eq:NN {       c }
 \cs_generate_variant:Nn \muskip_gset_eq:NN { Nc , cc }
@@ -1986,30 +2089,20 @@
 % \begin{macro}{\muskip_gsub:Nn, \muskip_gsub:cn}
 %   Using |by| here deals with the (incorrect) case |\muskip123|.
 %    \begin{macrocode}
-\__debug_patch_args:nNNpn
-  {
-    {#1}
-    {
-      \__debug_chk_expr:nNnN {#2} \etex_muexpr:D
-        { \etex_mutoglue:D } \muskip_add:Nn
-    }
-  }
+\@@_tmp:w \__debug_chk_var_local:N
 \cs_new_protected:Npn \muskip_add:Nn #1#2
   { \tex_advance:D #1 by \etex_muexpr:D #2 \scan_stop: }
-\cs_new_protected:Npn \muskip_gadd:Nn { \tex_global:D \muskip_add:Nn }
+\@@_tmp:w \__debug_chk_var_global:N
+\cs_new_protected:Npn \muskip_gadd:Nn #1#2
+  { \tex_global:D \tex_advance:D #1 by \etex_muexpr:D #2 \scan_stop: }
 \cs_generate_variant:Nn \muskip_add:Nn  { c }
 \cs_generate_variant:Nn \muskip_gadd:Nn { c }
-\__debug_patch_args:nNNpn
-  {
-    {#1}
-    {
-      \__debug_chk_expr:nNnN {#2} \etex_muexpr:D
-        { \etex_mutoglue:D } \muskip_sub:Nn
-    }
-  }
+\@@_tmp:w \__debug_chk_var_local:N
 \cs_new_protected:Npn \muskip_sub:Nn #1#2
   { \tex_advance:D #1 by - \etex_muexpr:D #2 \scan_stop: }
-\cs_new_protected:Npn \muskip_gsub:Nn { \tex_global:D \muskip_sub:Nn }
+\@@_tmp:w \__debug_chk_var_global:N
+\cs_new_protected:Npn \muskip_gsub:Nn #1#2
+  { \tex_global:D \tex_advance:D #1 by - \etex_muexpr:D #2 \scan_stop: }
 \cs_generate_variant:Nn \muskip_sub:Nn  { c }
 \cs_generate_variant:Nn \muskip_gsub:Nn { c }
 %    \end{macrocode}
@@ -2058,7 +2151,7 @@
 %   muskip expressions: this gives a more unified output.
 %    \begin{macrocode}
 \cs_new_protected:Npn \muskip_show:n
-  { \__msg_show_wrap:Nn \muskip_eval:n }
+  { \msg_show_eval:Nn \muskip_eval:n }
 %    \end{macrocode}
 % \end{macro}
 %
@@ -2068,7 +2161,7 @@
 \cs_new_eq:NN \muskip_log:N \__kernel_register_log:N
 \cs_new_eq:NN \muskip_log:c \__kernel_register_log:c
 \cs_new_protected:Npn \muskip_log:n
-  { \__msg_log_next: \muskip_show:n }
+  { \msg_log_eval:Nn \muskip_eval:n }
 %    \end{macrocode}
 % \end{macro}
 %