# New Ticket Created by Richard A Hogaboom
# Please include the string: [perl #133246]
# in the subject line of all future correspondence about this issue.
# <URL: https://rt.perl.org/Ticket/Display.html?id=133246 >
Attached is an executable file that demos a possible Perl 6 OO bug if
attributes and method names are the same. This includes some compile
time errors and an infinite loop.
--
Richard A Hogaboom
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# Richard Hogaboom
# richard.hogab...@gmail.com
# Fedora 28
# Perl 6 2018.04
# uname -a
# Linux new-host-3 4.16.12-300.fc28.x86_64 #1 SMP Fri May 25 21:13:28 UTC 2018
x86_64 x86_64 x86_64 GNU/Linux
# in Perl 6 OO if you have in a class an attribute name and a method name that
are the same,
# some errors may result or not - including compile time errors and an infinite
loop. just
# comment in the various examples one by one to run them individually.
use v6;
=begin pod
# EXAMPLE 1
# this works
class Address {
has $.var is rw;
}
my $addr = Address.new;
$addr.var = 'VAR';
say $addr.var;
=end pod
=begin pod
# EXAMPLE 2
# this works
class Address {
has $.var is rw;
multi method var() {
return $!var;
}
multi method var(Str $v) {
$!var = $v;
}
}
my $addr = Address.new;
$addr.var('VAR');
say $addr.var();
=end pod
=begin pod
# EXAMPLE 3
# adding a method of the same name as the attribute gives:
# Cannot modify an immutable Str (Nil)
# in block <unit> at t.p6 line 66
class Address {
has $.var is rw;
method var() {
}
}
my $addr = Address.new;
$addr.var = 'VAR';
say $addr.var;
# is there a general prohibition on having an attribute and an explicit method
of the same name?
=end pod
=begin pod
# EXAMPLE 4
# adding a return statement in the var() method gives a hang.
# using top shows the moar process at 100% CPU.
class Address {
has $.var is rw;
method var() {
return $.var;
}
}
my $addr = Address.new;
$addr.var = 'VAR';
say $addr.var;
# why does just adding a return statement eliminate the compile error? and hang?
# either this should not compile or a run time error should occur, not an
infinite loop.
# adding 'multi' to 'method var() {' above does not help.
=end pod
=begin pod
# EXAMPLE 5
# changing only $.var to $!var in the var() method gives:
# Cannot assign to a readonly variable or a value
# in block <unit> at t.p6 line 109
class Address {
has $.var is rw;
method var() {
return $!var;
}
}
my $addr = Address.new;
$addr.var = 'VAR';
say $addr.var;
# this eliminates the infinite loop , but returns to the previous readonly
variable msg.
=end pod
# all this seems a caution against using the same name as an attribute and
explicit method name,
# but shouldn't there be some type of prohibition/warning?
