ksh -n: remove linter warning for | & ; < > inside ${...}

On Usenet in comp.unix.shell, Janis Papanagnou
<[email protected]> reported:

> With syntax-check ('ksh -n') I get a warning in Ksh for this
> expression
>
>   "${pipe#* | }"
>
> concerning the pipe symbol. (Bash and Zsh don't complain.)
>
> (2709)$ ksh -n -c '"${pipe#* | }"'
> ksh: warning: line 1: | within ${} should be quoted
> (2710)$ ksh -n -c '"${pipe#* [|] }"'
> ksh: warning: line 1: | within ${} should be quoted
> (2711)$ ksh -n -c '"${pipe#* \| }"'

This is very strange. Neither POSIX nor any existing shell requires
'|' to be quoted in that context. ksh also works fine without
quoting it.

In lexstates.h, we find a clue to the reason:

    #define S_META 35
	/* | & ; < > inside ${...} reserved for future use */

Those AT&T plans for future use (whatever they might have been)
never materialised, and I have no such plans -- particularly as
requiring quoting there to avoid hypothetical new features would be
a backward incompatibility with POSIX and with historic ksh usage.

A look at ast-open-archive shows that these had been 'reserved for
future use' since the earliest version of that repo, so since
1995-08-28 or before. Yet another thing AT&T simply forgot about.

src/cmd/ksh93/sh/lex.c,
src/cmd/ksh93/data/lexstates.c,
src/cmd/ksh93/include/lexstates.h:
- sh_lex(): Remove the warning in question, e_lexusequote
  (separately for ';' and the other four).
- Remove e_lexusequote message with the text for that warning.
- Remove S_META state, which was only used in the ST_NESTED state
  table for this warning.
- Remove nested_tilde flag from the lexd struct, which was used to
  avoid the warning within ~(...) (pattern options) within ${...}.

Further discussion:
https://comp.unix.shell.narkive.com/H5Rfs3q8/ksh-warning-pipe-symbol-within-should-be-quoted

Author: McDutchie

src/cmd/ksh93/data/lexstates.c

@@ -353,7 +353,7 @@ static const char sh_lexstate5[256] =
 	0,	0,	0,	0,	0,	0,	0,	0,
 
   /*	space	!	"	#	$	%	&	'	*/
-	S_BLNK,	0,	S_QUOTE,0,	S_DOL,	0,	S_META,	S_LIT,
+	S_BLNK,	0,	S_QUOTE,0,	S_DOL,	0,	0,	S_LIT,
 
   /*	(	)	*	+	,	-	.	/	*/
 	S_PUSH,	S_POP,	0,	0,	0,	0,	0,	0,
@@ -362,7 +362,7 @@ static const char sh_lexstate5[256] =
 	0,	0,	0,	0,	0,	0,	0,	0,
 
   /*	8	9	:	;	<	=	>	?	*/
-	0,	0,	0,	S_POP,	S_META,	0,	S_META,	0,
+	0,	0,	0,	S_POP,	0,	0,	0,	0,
 
   /*	@	A	B	C	D	E	F	G	*/
 	0,	0,	0,	0,	0,	0,	0,	0,
@@ -386,7 +386,7 @@ static const char sh_lexstate5[256] =
 	0,	0,	0,	0,	0,	0,	0,	0,
 
   /*	x	y	z	{	|	}	~	del	*/
-	0,	0,	0,	S_BRACE,S_META,	S_POP,	S_TILDE,0
+	0,	0,	0,	S_BRACE,0,	S_POP,	S_TILDE,0
 };
 
 /*
@@ -752,7 +752,6 @@ const char e_lexobsolete4[]	= "line %d: [[ ... %s ... ]] obsolete, use ((... %s
 const char e_lexobsolete5[]	= "line %d: set %s obsolete";
 const char e_lexobsolete6[]	= "line %d: `{' instead of `in' is obsolete";
 const char e_lexusebrace[]	= "line %d: use braces to avoid ambiguities with $id[...]";
-const char e_lexusequote[]	= "line %d: %c within ${} should be quoted";
 const char e_lexescape[]	= "line %d: escape %c to avoid ambiguities";
 const char e_lexquote[]		= "line %d: quote %c to avoid ambiguities";
 const char e_lexnested[]	= "line %d: spaces required for nested subshell";

src/cmd/ksh93/include/lexstates.h

@@ -49,7 +49,6 @@
 #define S_EDOL	32	/* ends $identifier */
 #define S_BRACE	33	/* left brace */
 #define S_DOT	34	/* . char */
-#define S_META	35	/* | & ; < > inside ${...} reserved for future use */
 #define S_SPACE	S_BREAK	/* IFS space characters */
 #define S_DELIM	S_RES	/* IFS delimiter characters */
 #define S_MBYTE S_NAME	/* IFS first byte of multi-byte char */
@@ -149,7 +148,6 @@ extern const char e_lexobsolete4[];
 extern const char e_lexobsolete5[];
 extern const char e_lexobsolete6[];
 extern const char e_lexusebrace[];
-extern const char e_lexusequote[];
 extern const char e_lexescape[];
 extern const char e_lexquote[];
 extern const char e_lexnested[];

src/cmd/ksh93/include/shlex.h

@@ -50,7 +50,6 @@ struct _shlex_pvt_lexdata_
 	char		dolparen_arithexp;	/* set while comsub() is lexing an arithmetic expansion */
 	char		nest;
 	char		docword;
-	char		nested_tilde;
 	char 		*docend;
 	char		inlexskip;	/* set when sh_lex() is called from sh_lexskip() */
 	char		warn;

src/cmd/ksh93/include/version.h

@@ -18,7 +18,7 @@
 #include <ast_release.h>
 #include "git.h"
 
-#define SH_RELEASE_DATE	"2025-05-31"	/* must be in this format for $((.sh.version)) */
+#define SH_RELEASE_DATE	"2025-06-08"	/* must be in this format for $((.sh.version)) */
 /*
  * This comment keeps SH_RELEASE_DATE a few lines away from SH_RELEASE_SVER to avoid
  * merge conflicts when cherry-picking dev branch commits onto a release branch.

src/cmd/ksh93/sh/lex.c

@@ -660,10 +660,7 @@ int sh_lex(Lex_t* lp)
 				if(c=='~' && mode==ST_NESTED)
 				{
 					if(endchar(lp)==RBRACE)
-					{
-						lp->lexd.nested_tilde++;
 						goto tilde;
-					}
 					continue;
 				}
 				/* FALLTHROUGH */
@@ -686,19 +683,9 @@ int sh_lex(Lex_t* lp)
 				n = fcgetc();
 				if(n>0)
 				{
-					if(c=='~' && n==LPAREN)
-					{
-						if(lp->lexd.nested_tilde)
-							lp->lexd.nested_tilde++;
-						else if(lp->lex.incase)
-							lp->lex.incase = TEST_RE;
-					}
+					if(c=='~' && n==LPAREN && lp->lex.incase)
+						lp->lex.incase = TEST_RE;
 					fcseek(-LEN);
-					if(lp->lexd.nested_tilde)
-					{
-						lp->lexd.nested_tilde--;
-						continue;
-					}
 				}
 				if(n==LPAREN)
 					goto epat;
@@ -1038,10 +1025,6 @@ int sh_lex(Lex_t* lp)
 					fcseek(-LEN);
 				}
 				continue;
-			case S_META:
-				if(lp->lexd.warn && endchar(lp)==RBRACE && !lp->lexd.nested_tilde)
-					errormsg(SH_DICT,ERROR_warn(0),e_lexusequote,sh.inlineno,c);
-				continue;
 			case S_PUSH:
 				n = fcgetc();
 				if(n==RPAREN)
@@ -1080,14 +1063,8 @@ int sh_lex(Lex_t* lp)
 						fcseek(-LEN);
 					n = RPAREN;
 				}
-				if(c==RBRACE)
-					lp->lexd.nested_tilde = 0;
 				if(c==';' && n!=';')
-				{
-					if(lp->lexd.warn && n==RBRACE)
-						errormsg(SH_DICT,ERROR_warn(0),e_lexusequote,sh.inlineno,c);
 					continue;
-				}
 				if(mode==ST_QNEST)
 				{
 					if(lp->lexd.warn)