From @masak

<masak> rakudo​: class A { method pack($_) { s/c// }};
A.new.pack("ccc") # discovered by cono++
<p6eval> rakudo 220b67​: OUTPUT«Null PMC access in find_method('new') [...]
* masak submits rakudobug

Remove the s/c//, and everything works. Remove .pack("ccc"), and
everything works. How is it that the .pack call participates in
causing an error related to finding .new ?

From @coke

On Thu Jul 22 09​:58​:56 2010, masak wrote​:

<masak> rakudo​: class A { method pack($_) { s/c// }};
A.new.pack("ccc") # discovered by cono++
<p6eval> rakudo 220b67​: OUTPUT«Null PMC access in find_method('new') [...]
* masak submits rakudobug

Remove the s/c//, and everything works. Remove .pack("ccc"), and
everything works. How is it that the .pack call participates in
causing an error related to finding .new ?

21​:44 < [Coke]> rakudo​: class A { method pack($_) { s/c// }}; A.new.pack("ccc")
  # discovered by cono++
21​:44 <+p6eval> rakudo 7f5c22​: OUTPUT«Cannot modify readonly value␤ in
  '&infix​:<=>' at line 1␤ in 'A​::pack' at line
  22​:/tmp/HIyuNvbnYe␤ in main program body at line
  22​:/tmp/HIyuNvbnYe␤»

--
Will "Coke" Coleda

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

From @coke

On Tue Jul 27 18​:45​:07 2010, coke wrote​:

On Thu Jul 22 09​:58​:56 2010, masak wrote​:

<masak> rakudo​: class A { method pack($_) { s/c// }};
A.new.pack("ccc") # discovered by cono++
<p6eval> rakudo 220b67​: OUTPUT«Null PMC access in find_method('new')
[...]
* masak submits rakudobug

Remove the s/c//, and everything works. Remove .pack("ccc"), and
everything works. How is it that the .pack call participates in
causing an error related to finding .new ?

21​:44 < [Coke]> rakudo​: class A { method pack($_) { s/c// }};
A.new.pack("ccc")
# discovered by cono++
21​:44 <+p6eval> rakudo 7f5c22​: OUTPUT«Cannot modify readonly value␤
in
'&infix​:<=>' at line 1␤ in 'A​::pack' at line
22​:/tmp/HIyuNvbnYe␤ in main program body at line
22​:/tmp/HIyuNvbnYe␤»

Pretty much unchanged. Is this closable with tests now?

19​:37 < [Coke]> rakudo​: class A { method pack($_) { s/c// }}; A.new.pack("ccc")
19​:37 <+p6eval> rakudo 38907e​: OUTPUT«Cannot assign to a readonly variable or a
  value␤ in sub infix​:<=> at src/gen/CORE.setting​:7361␤ in
  method pack at /tmp/5h1grLXx6g​:1␤ in block <anon> at
  /tmp/5h1grLXx6g​:1␤ in <anon> at /tmp/5h1grLXx6g​:1␤»

--
Will "Coke" Coleda

From @masak

On Mon Oct 10 16​:38​:39 2011, coke wrote​:

On Tue Jul 27 18​:45​:07 2010, coke wrote​:

On Thu Jul 22 09​:58​:56 2010, masak wrote​:

<masak> rakudo​: class A { method pack($_) { s/c// }};
A.new.pack("ccc") # discovered by cono++
<p6eval> rakudo 220b67​: OUTPUT«Null PMC access in
find_method('new')
[...]
* masak submits rakudobug

Remove the s/c//, and everything works. Remove .pack("ccc"), and
everything works. How is it that the .pack call participates in
causing an error related to finding .new ?

21​:44 < [Coke]> rakudo​: class A { method pack($_) { s/c// }};
A.new.pack("ccc")
# discovered by cono++
21​:44 <+p6eval> rakudo 7f5c22​: OUTPUT«Cannot modify readonly value␤
in
'&infix​:<=>' at line 1␤ in 'A​::pack' at line
22​:/tmp/HIyuNvbnYe␤ in main program body at line
22​:/tmp/HIyuNvbnYe␤»

Pretty much unchanged. Is this closable with tests now?

19​:37 < [Coke]> rakudo​: class A { method pack($_) { s/c// }};
A.new.pack("ccc")
19​:37 <+p6eval> rakudo 38907e​: OUTPUT«Cannot assign to a readonly
variable or a
value␤ in sub infix​:<=> at src/gen/CORE.setting​:7361␤
in
method pack at /tmp/5h1grLXx6g​:1␤ in block <anon> at
/tmp/5h1grLXx6g​:1␤ in <anon> at /tmp/5h1grLXx6g​:1␤»

It doesn't Null PMC Access any more, so I'm happy. Leaving open in case
someone decides it needs tests, too.

From @moritz

fwiw the error is correct, because $_ is read-only (because it's a
parameter, and because "ccc" is a literal, and as such immutable).

Tested in subst.t

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