Re: [perl #7615] (if|unless) ( local ... ) not undone

On Sat, May 26, 2012 at 06:10:39PM -0700, James E Keenan via RT wrote:
> On Sat Sep 10 14:08:31 2005, schwern wrote:
> > On Fri, Aug 26, 2005 at 09:06:50AM -0700, Steve Peters via RT wrote:
> > > > $a = 10;
> > > > if (local $a = 1){
> > > > }
> > > > print $a; # Should be 10, not 1
> > 
> > Still busted in 5.8.6 and blead.
> > 
> > $ bleadperl -wle '$a = 10;  if( local $a = 1 ) {}  print $a'
> > Found = in conditional, should be == at -e line 1.
> > 1
> > $ bleadperl -wle '$a = 10;  if( my $a = 1 ) {}  print $a'
> > Found = in conditional, should be == at -e line 1.
> > 10
> > 
> > 
> 
> And still busted in 5.16.0.

The comparison to lexical vars is slightly misleading; its actually
lexical vars which are the more broken: the scope of the visibility of the
'my' declaration doesn't match the scope of when the lexical is actually
freed:

    sub DESTROY { warn "DESTROY(@_)\n" }

    {
	$x = 1;
	if (my $x = bless []) {
	    warn "in IF block: $x\n";
	}
	warn "exited IF block: $x\n";
    }
    warn "exited outer block: $x\n";

    warn "----\n";

    {
	$a = 1;

	if (local $a = 2) {
	    warn "in IF block: $a\n";
	}
	warn "exited IF block: $a\n";
    }
    warn "exited outer block: $a\n";

which outputs:

    in IF block: main=ARRAY(0x235bde8)
    exited IF block: 1
    DESTROY(main=ARRAY(0x235bde8))
    exited outer block: 1
    ----
    in IF block: 2
    exited IF block: 2
    exited outer block: 1

Here, the scope of when the lexical is freed and when the 'local' is
undone, is consistently at the end of the enclosing block, which could
arguably be viewed as correct; however the visibility of the lexical
*declaration* is only for the inner block.


-- 
"Do not dabble in paradox, Edward, it puts you in danger of fortuitous wit."
    -- Lady Croom, "Arcadia"

• [perl #7615] (if|unless) ( local ... ) not undone by Mike Guy
• [perl #7615] (if|unless) ( local ... ) not undone by Steve Peters via RT
• [perl #7615] (if|unless) ( local ... ) not undone by Steve Peters via RT
• Re: [perl #7615] (if|unless) ( local ... ) not undone by Michael G Schwern
• [perl #7615] (if|unless) ( local ... ) not undone by James E Keenan via RT
• Re: [perl #7615] (if|unless) ( local ... ) not undone by Dave Mitchell
• Re: [perl #7615] (if|unless) ( local ... ) not undone by Jesse Luehrs
• Re: [perl #7615] (if|unless) ( local ... ) not undone by Ronald J Kimball