When a hash isn't bound to an optional %-sigilled parameter, something weird ends up in it in Rakudo

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Migrated from rt.perl.org#79642 (status was 'resolved')

Searchable as RT79642$

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From @masak

<masak> rakudo​: sub foo($a, %h?) { bar($a, %h) }; sub bar($a, %h?) {
say "alive!" }; foo(42)
<p6eval> rakudo : OUTPUT«Method 'HOW' not found for invocant of class
'Hash'␤ in 'bar' at line 1 [...]
<masak> rakudo​: sub foo($a, %h?) { say %h.WHAT }; foo(42)
<p6eval> rakudo : OUTPUT«Method 'WHAT' not found for invocant of class
'Hash'␤ in 'foo' at line 22​:/tmp/qK5WsYzzEI␤ in main program body at
line 22​:/tmp/qK5WsYzzEI␤»
* masak submits rakudobug
<colomon> masak++
<masak> bug brought to you courtesy of a November being brought back
from the Mostly Dead.

Further experimenting reveals that the %h coming in through &foo
claims to be a Hash, but it has no methods at all, so you can't do
anything with it, not even pass it to &bar.

[p6rt]

From @masak

On Mon Nov 22 16​:06​:07 2010, masak wrote​:

<masak> rakudo​: sub foo($a, %h?) { bar($a, %h) }; sub bar($a, %h?) {
say "alive!" }; foo(42)
<p6eval> rakudo : OUTPUT«Method 'HOW' not found for invocant of class
'Hash'␤ in 'bar' at line 1 [...]
<masak> rakudo​: sub foo($a, %h?) { say %h.WHAT }; foo(42)
<p6eval> rakudo : OUTPUT«Method 'WHAT' not found for invocant of class
'Hash'␤ in 'foo' at line 22​:/tmp/qK5WsYzzEI␤ in main program body at
line 22​:/tmp/qK5WsYzzEI␤»
* masak submits rakudobug
<colomon> masak++
<masak> bug brought to you courtesy of a November being brought back
from the Mostly Dead.

Further experimenting reveals that the %h coming in through &foo
claims to be a Hash, but it has no methods at all, so you can't do
anything with it, not even pass it to &bar.

<masak> ah, here's a workaround​:
<masak> rakudo​: sub foo($a, %h = {}) { bar($a, %h) }; sub bar($a, %h?) { say "alive!" }; foo(42)
<p6eval> rakudo : OUTPUT«alive!␤»
<masak> of course.
* masak adds that to the ticket

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@masak - Status changed from 'new' to 'open'

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From @coke

On Mon Nov 22 16​:06​:07 2010, masak wrote​:

<masak> rakudo​: sub foo($a, %h?) { bar($a, %h) }; sub bar($a, %h?) {
say "alive!" }; foo(42)
<p6eval> rakudo : OUTPUT«Method 'HOW' not found for invocant of class
'Hash'␤ in 'bar' at line 1 [...]
<masak> rakudo​: sub foo($a, %h?) { say %h.WHAT }; foo(42)
<p6eval> rakudo : OUTPUT«Method 'WHAT' not found for invocant of class
'Hash'␤ in 'foo' at line 22​:/tmp/qK5WsYzzEI␤ in main program body
at
line 22​:/tmp/qK5WsYzzEI␤»
* masak submits rakudobug
<colomon> masak++
<masak> bug brought to you courtesy of a November being brought back
from the Mostly Dead.

Further experimenting reveals that the %h coming in through &foo
claims to be a Hash, but it has no methods at all, so you can't do
anything with it, not even pass it to &bar.

Fixed​:

16​:35 < [Coke]> rakudo​: sub foo($a, %h?) { bar($a, %h) }; sub bar($a,
%h?) {say
  "alive!" }; foo(42)
16​:35 -!- pothos_ is now known as pothos
16​:35 <+p6eval> rakudo 88c5a5​: OUTPUT«alive!␤»
16​:35 < [Coke]> rakudo​: sub foo($a, %h?) { say %h.WHAT }; foo(42)
16​:36 <+p6eval> rakudo 88c5a5​: OUTPUT«Hash()␤»

Closable with tests.

--
Will "Coke" Coleda

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From @moritz

Now tested in S06-signature/optional.t.

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