For now, forbid all list assignment initialisation of state variables,

as the precise semantics in Perl 6 are not clear. Better to make it a
syntax error, than to have one behaviour now, but change it later.
[I believe that this is the consensus. If not, it will be backed out]

p4raw-id: //depot/perl@31824

diff --git a/op.c b/op.c
index 6975d83..ca488a2 100644 (file)
--- a/op.c
+++ b/op.c
@@ -3968,6 +3968,8 @@ Perl_newASSIGNOP(pTHX_ I32 flags, OP *left, I32 optype, OP *right)
     }
 
     if (is_list_assignment(left)) {
+       static const char no_list_state[] = "Initialization of state variables"
+           " in list context currently forbidden";
        OP *curop;
 
        PL_modcount = 0;
@@ -4061,6 +4063,54 @@ Perl_newASSIGNOP(pTHX_ I32 flags, OP *left, I32 optype, OP *right)
                o->op_private |= OPpASSIGN_COMMON;
        }
 
+       if ((left->op_type == OP_LIST
+            || (left->op_type == OP_NULL && left->op_targ == OP_LIST))) {
+           OP* lop = ((LISTOP*)left)->op_first;
+           while (lop) {
+               if (lop->op_type == OP_PADSV ||
+                   lop->op_type == OP_PADAV ||
+                   lop->op_type == OP_PADHV ||
+                   lop->op_type == OP_PADANY) {
+                   if (lop->op_private & OPpPAD_STATE) {
+                       if (left->op_private & OPpLVAL_INTRO) {
+                           /* Each variable in state($a, $b, $c) = ... */
+                       }
+                       else {
+                           /* Each state variable in
+                              (state $a, my $b, our $c, $d, undef) = ... */
+                       }
+                       yyerror(no_list_state);
+                   } else {
+                       /* Each my variable in
+                          (state $a, my $b, our $c, $d, undef) = ... */
+                   }
+               } else {
+                   /* Other ops in the list. undef may be interesting in
+                      (state $a, undef, state $c) */
+               }
+               lop = lop->op_sibling;
+           }
+       }
+       else if (((left->op_private & (OPpLVAL_INTRO | OPpPAD_STATE))
+                   == (OPpLVAL_INTRO | OPpPAD_STATE))
+               && (   left->op_type == OP_PADSV
+                   || left->op_type == OP_PADAV
+                   || left->op_type == OP_PADHV
+                   || left->op_type == OP_PADANY))
+       {
+           /* All single variable list context state assignments, hence
+              state ($a) = ...
+              (state $a) = ...
+              state @a = ...
+              state (@a) = ...
+              (state @a) = ...
+              state %a = ...
+              state (%a) = ...
+              (state %a) = ...
+           */
+           yyerror(no_list_state);
+       }
+
        if (right && right->op_type == OP_SPLIT && !PL_madskills) {
            OP* tmpop = ((LISTOP*)right)->op_first;
            if (tmpop && (tmpop->op_type == OP_PUSHRE)) {

diff --git a/pod/perldiag.pod b/pod/perldiag.pod
index cd741ab..9123a01 100644 (file)
--- a/pod/perldiag.pod
+++ b/pod/perldiag.pod
@@ -1999,6 +1999,13 @@ either consume text or fail.
 The <-- HERE shows in the regular expression about where the problem was
 discovered.
 
+=item Initialization of state variables in list context currently forbidden
+
+(F) Currently the implementation of "state" only permits the initialization
+of scalar variables in scalar context. Re-write C<state ($a) = 42> as
+C<state $a = 42> to change from list to scalar context. Constructions such
+as C<state (@a) = foo()> will be supported in a future perl release.
+
 =item Insecure dependency in %s
 
 (F) You tried to do something that the tainting mechanism didn't like.

diff --git a/t/op/state.t b/t/op/state.t
index 7be1666..6d835c4 100644 (file)
--- a/t/op/state.t
+++ b/t/op/state.t
@@ -10,7 +10,7 @@ BEGIN {
 use strict;
 use feature ":5.10";
 
-plan tests => 108;
+plan tests => 117;
 
 ok( ! defined state $uninit, q(state vars are undef by default) );
 
@@ -301,17 +301,6 @@ foreach my $x (0 .. 4) {
 
 
 #
-# List context reassigns, but scalar doesn't.
-#
-my @swords = qw [Stormbringer Szczerbiec Grimtooth Corrougue];
-foreach my $sword (@swords) {
-    state ($s1) = state $s2 = $sword;
-    is $s1, $swords [0], 'mixed context';
-    is $s2, $swords [0], 'mixed context';
-}
-
-
-#
 # Use with given.
 #
 my @spam = qw [spam ham bacon beans];
@@ -331,3 +320,28 @@ foreach my $spam (@spam) {
     state $x = "two";
     is $x, "two", "masked"
 }
+
+foreach my $forbidden (<DATA>) {
+    chomp $forbidden;
+    no strict 'vars';
+    eval $forbidden;
+    like $@, qr/Initialization of state variables in list context currently forbidden/, "Currently forbidden: $forbidden";
+}
+__DATA__
+state ($a) = 1;
+(state $a) = 1;
+state @a = 1;
+state (@a) = 1;
+(state @a) = 1;
+state %a = ();
+state (%a) = ();
+(state %a) = ();
+state ($a, $b) = ();
+state ($a, @b) = ();
+(state $a, state $b) = ();
+(state $a, $b) = ();
+(state $a, my $b) = ();
+(state $a, state @b) = ();
+(state $a, local @b) = ();
+(state $a, undef, state $b) = ();
+state ($a, undef, $b) = ();