From publiustemp-perl6users@yahoo.com

  subset Letter of Str where { $_ =~ /^ <[a..z]> $/ };

  my $first_letter = 'a';
  say $first_letter;

  my Letter $second_letter = 'a';
  say $second_letter;

  sub doit (Letter $letter) {
  say $letter;
  }

  doit('a');

That outputs (_block69 is the second 'say' and the 'Cannot assign' is the sub call)​:

a
_block69
Cannot assign to readonly variable.
current instr.​: 'die' pc 14740 (src/builtins/control.pir​:204)
called from Sub 'infix​:=' pc 13106 (src/builtins/assign.pir​:24)
called from Sub '_block62' pc 310 (EVAL_14​:128)
called from Sub '!SUBTYPE_ACCEPTS' pc 15909 (src/builtins/guts.pir​:237)
called from Sub '!TYPECHECKPARAM' pc 15676 (src/builtins/guts.pir​:128)
called from Sub 'doit' pc 527 (EVAL_14​:212)
called from Sub '_block14' pc 200 (EVAL_14​:83)
called from Sub '!UNIT_START' pc 16073 (src/builtins/guts.pir​:327)
called from Sub 'parrot;PCT;HLLCompiler;eval' pc 892 (src/PCT/HLLCompiler.pir​:508)
called from Sub 'parrot;PCT;HLLCompiler;evalfiles' pc 1217 (src/PCT/HLLCompiler.pir​:669)
called from Sub 'parrot;PCT;HLLCompiler;command_line' pc 1398 (src/PCT/HLLCompiler.pir​:759)
called from Sub 'parrot;Perl6;Compiler;main' pc 18981 (perl6.pir​:162)
perl6(8003) malloc​: *** error for object 0x2bcc680​: double free
*** set a breakpoint in malloc_error_break to debug

My info​:

$ svn info; uname -a
Path​: .
URL​: https://svn.perl.org/parrot/trunk
Repository Root​: https://svn.perl.org/parrot
Repository UUID​: d31e2699-5ff4-0310-a27c-f18f2fbe73fe
Revision​: 34446
Node Kind​: directory
Schedule​: normal
Last Changed Author​: kjs
Last Changed Rev​: 34446
Last Changed Date​: 2008-12-27 21​:17​:55 +0000 (Sat, 27 Dec 2008)

Darwin curtis-poes-computer-3.local 9.5.1 Darwin Kernel Version 9.5.1​: Fri Sep 19 16​:19​:24 PDT 2008; root​:xnu-1228.8.30~1/RELEASE_I386 i386

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From @jnthn

On Sat Dec 27 14​:08​:48 2008, publiustemp-perl6users@​yahoo.com wrote​:

subset Letter of Str where \{ $\_ =~ /^ \<\[a\.\.z\]> $/ \};

my $first\_letter = 'a';
say $first\_letter;

my Letter $second\_letter = 'a';
say $second\_letter;

sub doit \(Letter $letter\) \{
    say $letter;
\}

doit\('a'\);

That outputs (_block69 is the second 'say' and the 'Cannot assign' is
the sub call)​:

a
_block69
Cannot assign to readonly variable.

That's a Perl 5-o. :-) You likely meant​:

subset Letter of Str where { $_ ~~ /^ <[a..z]> $/ };

Which does work. But there are two issues​:

* We should implement the =~ check to give you a useful message about
this change. There's already a ticket for that one.

* I think both cases should give the "cannot assign to readonly
variable" warning because the $_ should be read-only inside that block.

So to resolve this ticket we should do the second of these.

Thanks,

Jonathan

The RT System itself - Status changed from 'new' to 'open'

From @jnthn

On Fri Feb 13 10​:06​:37 2009, jnthn@​jnthn.net wrote​:

On Sat Dec 27 14​:08​:48 2008, publiustemp-perl6users@​yahoo.com wrote​:

subset Letter of Str where \{ $\_ =~ /^ \<\[a\.\.z\]> $/ \};

\.\.\.snip\.\.\.

That's a Perl 5-o. :-) You likely meant​:

subset Letter of Str where { $_ ~~ /^ <[a..z]> $/ };

...snip...

* I think both cases should give the "cannot assign to readonly
variable" warning because the $_ should be read-only inside that block.

So to resolve this ticket we should do the second of these.

And as of git 0f87695 this now fails with the read-only error in all
cases, not just the second one. (It may well segfault after giving the
error, but that's a Parrot issue that we already have plenty of open
tickets for, so resolving this one).

Plus added tests. :-)

Thanks,

Jonathan

@jnthn - Status changed from 'open' to 'resolved'