Fix oddly specific syntax error corrupting subsequent [[ ... ]]

Reproducer:

    $ x=([x]=1 [y)
    -ksh: syntax error: `)' unexpected
    $ [[ -z $x ]]
    -ksh: [[ -z  ]]: not found

Any '[[' command following that syntax error will fail similarly;
the whole of it (after variable expansion) is incorrectly looked up
as a command name. The syntax error must be generated by an
associative array assignment (with or without an explicit typeset
-A) with at least one valid assignment element followed by an
invalid assignment element starting with '[' but not containing
']='.

This seems to be another bug that is in every ksh93 version ever.
I've confirmed that ksh 1993-12-28 s+ and ksh2020 fail identically.
Presumably, so does everything in between.

Analysis:

The syntax error function, sh_syntax(), calls lexopen() in mode 0
to reset the lexer state. There is a variable that isn't getting
reset there though it should be. Using systematic elimination I
found that the variable that needs to be reset is lp->assignok (set
"when name=value is legal"). If it is set, '[[' is not processed.

src/cmd/ksh93/sh/lex.c: lexopen():
- Reset 'assignok' in the lexer state (regardless of mode).
- In the mode 0 total lexer state reinit, several members of lexd
  (struct _shlex_pvt_lexdata_) were not getting reset; just memset
  the whole thing to zero.
     Note for backporters: this change requires commit da97587e to
  be correct. That commit took the stack size and pointer (lex_max
  and *lex_match) out of this struct; those should not be reset!

Resolves: https://github.com/ksh93/ksh/issues/486

NEWS

@@ -3,6 +3,11 @@ For full details, see the git log at: https://github.com/ksh93/ksh/tree/1.0
 
 Any uppercase BUG_* names are modernish shell bug IDs.
 
+2022-07-09:
+
+- Fixed a bug that broke '[[ ... ]]' test expressions for the command
+  following a syntax error in an associative array assignment.
+
 2022-07-05:
 
 - Fixed a spurious syntax error on encountering a process substitution

src/cmd/ksh93/include/version.h

@@ -23,7 +23,7 @@
 
 #define SH_RELEASE_FORK	"93u+m"		/* only change if you develop a new ksh93 fork */
 #define SH_RELEASE_SVER	"1.0.0-beta.2"	/* semantic version number: https://semver.org */
-#define SH_RELEASE_DATE	"2022-07-05"	/* must be in this format for $((.sh.version)) */
+#define SH_RELEASE_DATE	"2022-07-09"	/* must be in this format for $((.sh.version)) */
 #define SH_RELEASE_CPYR	"(c) 2020-2022 Contributors to ksh " SH_RELEASE_FORK
 
 /* Scripts sometimes field-split ${.sh.version}, so don't change amount of whitespace. */

src/cmd/ksh93/sh/lex.c

@@ -208,20 +208,11 @@ Lex_t *sh_lexopen(Lex_t *lp, int mode)
 	if(!lp)
 		lp = (Lex_t*)sh_newof(0,Lex_t,1,0);
 	fcnotify(lex_advance,lp);
-	lp->lex.intest = lp->lex.incase = lp->lex.skipword = lp->lexd.warn = 0;
-	lp->comp_assign = 0;
+	lp->lex.intest = lp->lex.incase = lp->lex.skipword = lp->comp_assign = lp->comsub = lp->assignok = 0;
 	lp->lex.reservok = 1;
-	if(!sh_isoption(SH_DICTIONARY) && sh_isoption(SH_NOEXEC))
-		lp->lexd.warn=1;
 	if(!mode)
-	{
-		lp->lexd.noarg = lp->lexd.level= lp->lexd.dolparen = 0;
-		lp->lexd.nocopy = lp->lexd.docword = lp->lexd.nest = lp->lexd.paren = 0;
-		lp->lexd.lex_state = lp->lexd.lastc=0;
-		lp->lexd.docend = 0;
-		lp->lexd.nested_tilde = 0;
-	}
-	lp->comsub = 0;
+		memset(&lp->lexd,0,sizeof(struct _shlex_pvt_lexdata_));
+	lp->lexd.warn = !sh_isoption(SH_DICTIONARY) && sh_isoption(SH_NOEXEC);
 	return(lp);
 }
 

src/cmd/ksh93/tests/bracket.sh

@@ -494,5 +494,14 @@ $SHELL -c '[[ c < b ]]'; got=$?
 ((exp == got)) || err_exit "[[ ... ]] cannot handle 'c < b'" \
 	"(expected $exp, got $got)"
 
+# ======
+# https://github.com/ksh93/ksh/issues/486
+unset x
+savePATH=$PATH
+PATH=/dev/null
+command eval 'x=([x]=1 [y)' 2>/dev/null
+[[ -z $x ]] 2>/dev/null || err_exit "[[ ... ]] breaks after syntax error in associative array assignment (got status $?)"
+PATH=$savePATH
+
 # ======
 exit $((Errors<125?Errors:125))