Two small improvements for named indexes U-Z

tabularray.sty

@@ -84,6 +84,7 @@
   }
 
 \cs_generate_variant:Nn \msg_error:nnnn { nnVn }
+\cs_generate_variant:Nn \msg_error:nnnnn { nnnVV }
 \cs_generate_variant:Nn \prop_item:Nn { Ne, NV }
 \cs_generate_variant:Nn \prop_put:Nnn { Nxn, Nxx, NxV }
 \cs_generate_variant:Nn \regex_replace_all:NnN { NVN }
@@ -877,14 +878,15 @@
 \cs_new_protected:Npn \__tblr_child_selector_odd_or_even:nn #1 #2
   {
     \seq_set_split:Nnn \l_tmpa_seq {-} { #2 - Z }
-    \tl_set:Nx \l__tblr_child_from_tl { \seq_item:Nn \l_tmpa_seq {1} }
-    \tl_set:Nx \l__tblr_child_to_tl { \seq_item:Nn \l_tmpa_seq {2} }
+    \__tblr_child_name_to_index:eN { \seq_item:Nn \l_tmpa_seq {1} }
+      \l__tblr_child_from_tl
+    \__tblr_child_name_to_index:eN { \seq_item:Nn \l_tmpa_seq {2} }
+      \l__tblr_child_to_tl
     \tl_use:c { int_if_ #1 :nF } { \l__tblr_child_from_tl }
       {
         \tl_set:Nx \l__tblr_child_from_tl
           { \int_eval:n { \l__tblr_child_from_tl + 1 } }
       }
-    \__tblr_child_name_to_index:VN \l__tblr_child_to_tl \l__tblr_child_to_tl
     \int_step_inline:nnnn { \l__tblr_child_from_tl } {2} { \l__tblr_child_to_tl }
       { \clist_put_right:Nn \l_tblr_childs_clist {##1} }
   }
@@ -942,17 +944,26 @@
 
 \regex_const:Nn \c__tblr_child_name_regex { ^ [U-Z] $ }
 
+\msg_new:nnn { tabularray } { named-index-out-of-bound }
+  { Named ~ index ~ ``#1'' ~ (#2) ~ out ~ of ~ bound ~ [1, ~ #3].  }
+
 %% Convert U, V, W, X, Y, Z to the indexes of the last six childs, respectively
 \cs_new_protected_nopar:Npn \__tblr_child_name_to_index:nN #1 #2
   {
     \regex_match:NnTF \c__tblr_child_name_regex {#1}
       {
         \tl_set:Nx #2
           { \int_eval:n { \l_tblr_childs_total_tl + \int_from_alph:n {#1} - 26 } }
+        \int_compare:nNnT #2 < 1
+          {
+            \msg_error:nnnVV { tabularray } { named-index-out-of-bound }
+              {#1} {#2} {\l_tblr_childs_total_tl}
+            \tl_set:Nn #2 {1}
+          }
       }
       { \tl_set:Nx #2 { #1 } }
   }
-\cs_generate_variant:Nn \__tblr_child_name_to_index:nN { VN }
+\cs_generate_variant:Nn \__tblr_child_name_to_index:nN { VN, eN }
 
 %%% --------------------------------------------------------
 %%> \section{New Table Commands}

testfiles/extra-002.md5

@@ -1 +1 @@
-5e1656f7611de36d23ef861c609ba7e8
+9d7895b1283ee571643baaf1b0828fd4

testfiles/extra-002.tex

@@ -93,4 +93,25 @@
 \end{tblr}
 \ENDTEST
 
+\bigskip\hrule\bigskip
+
+\BEGINTEST{named indexes U-Z in child from}
+\begin{tblr}{
+  hlines, vlines,
+  cell{-}{even[X-Z]}={preto=x}
+}
+  & & & \\
+\end{tblr}
+\ENDTEST
+
+\bigskip\hrule\bigskip
+
+\BEGINTEST{name indexes U-Z ensured positive}
+\begin{tblr}{
+  hlines, vlines,
+  cell{-}{U-Z}={preto=x}
+}
+  & & & \\
+\end{tblr}
+\ENDTEST
 \end{document}

testfiles/extra-002.tlg

@@ -12,5 +12,21 @@ LaTeX Font Info:    External font `cmex10' loaded for size
 TEST 2: named indexes U-Z
 ============================================================
 ============================================================
+============================================================
+TEST 3: named indexes U-Z in child from
+============================================================
+============================================================
+============================================================
+TEST 4: name indexes U-Z ensured positive
+============================================================
+! Package tabularray Error: Named index ``U'' (-1) out of bound [1, 4].
+Type <return> to continue.
+ ...                                              
+l. ...\end
+          {tblr}
+LaTeX does not know anything more about this error, sorry.
+Try typing <return> to proceed.
+If that doesn't work, type X <return> to quit.
+============================================================
 [1
 ] (extra-002.aux)