TSa Thomas.Sandlass-at-vts-systems.de |Perl 6| wrote:
class A
{
has $.foo = "A";
has $!bar = "A";
method blahh()
{
say $.foo ~ $!foo ~ $!bar;
}
}
class B is A
{
has $.foo = "B";
has $!bar = "B";
}
my $a = A.new;
my $b = B.new;
say $a.blahh; # prints AAA
say $b.blahh; # prints BAA, right?
Shouldn't there be a warning in B that $!B::bar overwrites $!A::bar
without an accessor? And of course the example shows that $!foo in
blahh is not derivation friendly. Or am I getting things wrong and
there can be only one $!foo and $!bar in the namespace of the objects
created from A and B? That is the declarations in B are superfluous
if not outright wrong? Well, or they only affect the generated
constructor and the storage location is shared? The latter would
nicely contrast them to non twigil attributes in the form 'has $foo'.
A::!foo will be distinct from B::!foo. The accessor in B will override
the accessor from A. I would not mind a warning, since the
implementation knows what is going on being auto-generated. But in
general, if you write methods that are accessors, separate from the
backing data, the compiler can't tell what you meant and won't give any
warning.
--John
