Fix spurious syntax error in multidim. indexed array assignments

Example reproducers:
  $ my_array=((somevalue) (select)) && typeset -p my_array
  -ksh: syntax error: `select' unexpected
  $ my_array=((somevalue) select) && typeset -p my_array
  -ksh: syntax error: `select' unexpected

Analysis: The problem is in the assign() function in parse.c. From
the second value element on, reserved words/keywords are wrongly
recognised when assign() is called recursively to parse
multidimensional array assignments, because the lexer flag
'noreserv' is reset to zero in the course of the assign() call.

src/cmd/ksh93/sh/parse.c: assign():
- After recursively calling assign() to deal with nested
  parentheses, set noreserv to back to 1 to re-disable the
  recognition of reserved words by the lexer.

Thanks to @TristanJamesBall for the report.
Resolves: #790

NEWS

@@ -2,6 +2,14 @@ This documents significant changes in the dev branch of ksh 93u+m.
 For full details, see the git log at: https://github.com/ksh93/ksh
 Uppercase BUG_* IDs are shell bug IDs as used by the Modernish shell library.
 
+2024-10-23:
+
+- Fixed a bug in multidimensional indexed array assignments where unquoted
+  values that corresponded to reserved words (such as 'if' or 'select')
+  incorrectly caused a syntax error. For example,
+    my_array=((somevalue) select) && typeset -p my_array
+  now works as expected. This bug was introduced in ksh 93r+ 2006-06-30.
+
 2024-08-28:
 
 - Fixed a crash that occurred for an arithmetic 'for' that has two instead of

src/cmd/ksh93/include/version.h

@@ -18,7 +18,7 @@
 
 #define SH_RELEASE_FORK	"93u+m"		/* only change if you develop a new ksh93 fork */
 #define SH_RELEASE_SVER	"1.1.0-alpha"	/* semantic version number: https://semver.org */
-#define SH_RELEASE_DATE	"2024-08-28"	/* must be in this format for $((.sh.version)) */
+#define SH_RELEASE_DATE	"2024-10-23"	/* must be in this format for $((.sh.version)) */
 #define SH_RELEASE_CPYR	"(c) 2020-2024 Contributors to ksh " SH_RELEASE_FORK
 
 /* Scripts sometimes field-split ${.sh.version}, so don't change amount of whitespace. */

src/cmd/ksh93/sh/parse.c

@@ -1053,7 +1053,11 @@ static struct argnod *assign(Lex_t *lexp, struct argnod *ap, int type)
 			ar = stkfreeze(sh.stk,1);
 			ar->argnxt.ap = 0;
 			if(!aq)
+			{
 				ar = assign(lexp,ar,0);
+				/* since noreserv is reset to 0 below, we have set it again after a recursive call */
+				lexp->noreserv = 1;
+			}
 			ar->argflag |= ARG_MESSAGE;
 			*settail = ar;
 			settail = &(ar->argnxt.ap);

src/cmd/ksh93/tests/arrays2.sh

@@ -2,7 +2,7 @@
 #                                                                      #
 #               This software is part of the ast package               #
 #          Copyright (c) 1982-2012 AT&T Intellectual Property          #
-#          Copyright (c) 2020-2023 Contributors to ksh 93u+m           #
+#          Copyright (c) 2020-2024 Contributors to ksh 93u+m           #
 #                      and is licensed under the                       #
 #                 Eclipse Public License, Version 2.0                  #
 #                                                                      #
@@ -305,5 +305,25 @@ got=$(typeset -a arr=(a (b d e) c d e); echo ${arr[@]:2:${#arr[@]}-2})
 got=$(typeset -A arr=(a (b d e) c d e); echo ${arr[@]:2:${#arr[@]}-2})
 [[ $got == "$exp" ]] || err_exit "array slicing test 13 (expected $(printf %q "$exp"), got $(printf %q "$got"))"
 
+# ======
+# Reserved words as values
+# https://github.com/ksh93/ksh/issues/790
+got=$(set +x; eval 'typeset -a a1=((demo) (select) (if) (case) (while))' 2>&1 && typeset -p a1)
+exp='typeset -a a1=((demo) (select) (if) (case) (while) )'
+[[ $got == "$exp" ]] || err_exit "reserved word assigned as multidimensional array value" \
+	"(expected $(printf %q "$exp"), got $(printf %q "$got"))"
+got=$(set +x; eval 'typeset -a a1=((demo) (select) if case while)' 2>&1 && typeset -p a1)
+exp='typeset -a a1=((demo) (select) if case while)'
+[[ $got == "$exp" ]] || err_exit "reserved word assigned as top-level value in multidimensional array" \
+	"(expected $(printf %q "$exp"), got $(printf %q "$got"))"
+got=$(set +x; eval 'a1=((demo) (select) (if) (case) (while))' 2>&1 && typeset -p a1)
+exp='typeset -a a1=((demo) (select) (if) (case) (while) )'
+[[ $got == "$exp" ]] || err_exit "reserved word assigned as implicit multidimensional array value" \
+	"(expected $(printf %q "$exp"), got $(printf %q "$got"))"
+got=$(set +x; eval 'a1=((demo) (select) if case while)' 2>&1 && typeset -p a1)
+exp='typeset -a a1=((demo) (select) if case while)'
+[[ $got == "$exp" ]] || err_exit "reserved word assigned as top-level value in implicit multidimensional array" \
+	"(expected $(printf %q "$exp"), got $(printf %q "$got"))"
+
 # ======
 exit $((Errors<125?Errors:125))