# New Ticket Created by Patrick R. Michaud
# Please include the string: [perl #56622]
# in the subject line of all future correspondence about this issue.
# <URL: http://rt.perl.org/rt3/Ticket/Display.html?id=56622 >
This one takes a bit of lengthy explanation, but the bottom
line is that the 'isa' opcode can returns different results
when given a String PMC versus a string register or constant.
Here's a sample program, run against r29086 (the code is explained
below):
$ cat w2.pir
.sub main :main
.local pmc xyzns, xyzclass, xyzobj
xyzns = get_root_namespace ['foo';'XYZ']
xyzclass = newclass xyzns
xyzobj = new xyzclass
## prove that it's the correct type
xyzobj.'abc'()
## test two forms of isa
$P0 = new 'String'
$P0 = 'XYZ'
$I0 = isa xyzobj, 'XYZ'
say $I0
$I0 = isa xyzobj, $P0
say $I0
.end
.HLL 'foo', ''
.namespace ['XYZ']
.sub 'abc' :method
say 'XYZ::abc'
.end
This code is creating a class within another HLL namespace ('foo').
To do this we first get the ['foo';'XYZ'] namespace and use that as
an argument to the newclass opcode. We then use that class to
create xyzobj, and test that we can properly invoke the method.
After that we test "isa XYZ" using a string constant and a String PMC.
The output of the above program is:
$ ./parrot w2.pir
XYZ::abc
1
0
As you can see, the two 'isa' opcodes return different results.
This doesn't happen if 'isa' is being used from the same HLL
namespace as the class itself: If the .HLL line is moved to the
top of the file (thus placing sub 'main' in the same HLL namespace),
or if the .HLL line is removed and we change the get_root_namespace
line to read from ['parrot';'XYZ'], then the two isa opcodes return
the same value.
This report strictly questions the inconsistency of results
when 'isa' is given a string versus a String PMC, without any
comment about whether the above should be 0 in both cases or
1 in both cases. I can make an argument for either answer.
It's just that it seems the two forms of isa ought to return
the same answer, or that we make it clear why they differ.
Thanks!
Pm
