Add PM_DECLARED and PM_DECLAREDNULL parameter flags.

This addresses the issue that "typeset foo" creates $foo set to an
empty string, which differs from typeset handling in bash and ksh.
It does this by concealing the internal value rather than alter
the way internal values are defaulted.

This imposes the following changes:

A typeset variable with no assignment triggers NO_UNSET warnings
when the name is used in parameter expansion or math.

The typeset -AEFHLRTZailux options are applied upon the first
assignment to the variable.  Explicit unset before the first
assignment discards all of those properties.  If any option is
applied to an existing name, historic behavior is unchanged.

Consequent to the foregoing, the (t) parameter expansion flag
prints nothing until after the first assignment, and the (i)
and (I) subscript flags also print nothing.

The bash behavior of "unset foo; typeset -p foo" is NOT used.
This is called out as an emulation distinction, not a change.

The test cases have not been updated, so several now fail.
The test harness has been updated to declare default values.

Src/builtin.c

@@ -2491,6 +2491,7 @@ typeset_single(char *cname, char *pname, Param pm, UNUSED(int func),
 		return NULL;
 	    }
 	}
+	pm->node.flags |= PM_DECLAREDNULL;
     } else {
 	if (idigit(*pname))
 	    zerrnam(cname, "not an identifier: %s", pname);

Src/params.c

@@ -2093,7 +2093,8 @@ fetchvalue(Value v, char **pptr, int bracks, int flags)
 	if (sav)
 	    *s = sav;
 	*pptr = s;
-	if (!pm || (pm->node.flags & PM_UNSET))
+	if (!pm || ((pm->node.flags & PM_UNSET) &&
+		    !(pm->node.flags & PM_DECLARED)))
 	    return NULL;
 	if (v)
 	    memset(v, 0, sizeof(*v));
@@ -3055,6 +3056,7 @@ assignsparam(char *s, char *val, int flags)
 	     * Don't warn about anything.
 	     */
 	    flags &= ~ASSPM_WARN;
+	    v->pm->node.flags &= ~PM_DECLAREDNULL;
 	}
 	*ss = '[';
 	v = NULL;
@@ -3080,6 +3082,7 @@ assignsparam(char *s, char *val, int flags)
     }
     if (flags & ASSPM_WARN)
 	check_warn_pm(v->pm, "scalar", created, 1);
+    v->pm->node.flags &= ~PM_DECLAREDNULL;
     if (flags & ASSPM_AUGMENT) {
 	if (v->start == 0 && v->end == -1) {
 	    switch (PM_TYPE(v->pm->node.flags)) {
@@ -3232,6 +3235,7 @@ assignaparam(char *s, char **val, int flags)
 
     if (flags & ASSPM_WARN)
 	check_warn_pm(v->pm, "array", created, may_warn_about_nested_vars);
+    v->pm->node.flags &= ~PM_DECLAREDNULL;
 
     /*
      * At this point, we may have array entries consisting of
@@ -3444,6 +3448,7 @@ sethparam(char *s, char **val)
 	    return NULL;
 	}
     check_warn_pm(v->pm, "associative array", checkcreate, 1);
+    v->pm->node.flags &= ~PM_DECLAREDNULL;
     setarrvalue(v, val);
     unqueue_signals();
     return v->pm;
@@ -3515,6 +3520,7 @@ assignnparam(char *s, mnumber val, int flags)
 	if (flags & ASSPM_WARN)
 	    check_warn_pm(v->pm, "numeric", 0, 1);
     }
+    v->pm->node.flags &= ~PM_DECLAREDNULL;
     setnumvalue(v, val);
     unqueue_signals();
     return v->pm;
@@ -3619,6 +3625,7 @@ unsetparam_pm(Param pm, int altflag, int exp)
     else
 	altremove = NULL;
 
+    pm->node.flags &= ~PM_DECLARED;	/* like ksh, not like bash */
     if (!(pm->node.flags & PM_UNSET))
 	pm->gsu.s->unsetfn(pm, exp);
     if (pm->env)
@@ -5035,6 +5042,7 @@ arrfixenv(char *s, char **t)
 
     if (isset(ALLEXPORT))
 	pm->node.flags |= PM_EXPORTED;
+    pm->node.flags &= ~PM_DECLAREDNULL;
 
     /*
      * Do not "fix" parameters that were not exported
@@ -5839,8 +5847,9 @@ printparamnode(HashNode hn, int printflags)
     Param peer = NULL;
 
     if (p->node.flags & PM_UNSET) {
-	if (printflags & (PRINT_POSIX_READONLY|PRINT_POSIX_EXPORT) &&
-	    p->node.flags & (PM_READONLY|PM_EXPORTED)) {
+	if ((printflags & (PRINT_POSIX_READONLY|PRINT_POSIX_EXPORT) &&
+	     p->node.flags & (PM_READONLY|PM_EXPORTED)) ||
+	    (p->node.flags & PM_DECLAREDNULL) == PM_DECLAREDNULL) {
 	    /*
 	     * Special POSIX rules: show the parameter as readonly/exported
 	     * even though it's unset, but with no value.

Src/zsh.h

@@ -1931,6 +1931,8 @@ struct tieddata {
 #define PM_DONTIMPORT	(1<<22)	/* do not import this variable              */
 #define PM_RESTRICTED	(1<<23) /* cannot be changed in restricted mode     */
 #define PM_UNSET	(1<<24)	/* has null value                           */
+#define PM_DECLARED	(1<<17) /* */
+#define PM_DECLAREDNULL (PM_DECLARED|PM_UNSET)
 #define PM_REMOVABLE	(1<<25)	/* special can be removed from paramtab     */
 #define PM_AUTOLOAD	(1<<26) /* autoloaded from module                   */
 #define PM_NORESTORE	(1<<27)	/* do not restore value of local special    */

Test/runtests.zsh

@@ -7,7 +7,7 @@ emulate zsh
 # protect from catastrophic failure of an individual test.
 # We could probably do that with subshells instead.
 
-integer success failure skipped retval
+integer success=0 failure=0 skipped=0 retval
 for file in "${(f)ZTST_testlist}"; do
   $ZTST_exe +Z -f $ZTST_srcdir/ztst.zsh $file
   retval=$?

Test/ztst.zsh

@@ -60,7 +60,7 @@ ZTST_mainopts=(${(kv)options})
 ZTST_testdir=$PWD
 ZTST_testname=$1
 
-integer ZTST_testfailed
+integer ZTST_testfailed=0
 
 # This is POSIX nonsense.  Because of the vague feeling someone, somewhere
 # may one day need to examine the arguments of "tail" using a standard