From @masak

<szabgab> rakudo​: class X { has $.y is rw; sub qq() { say "sub $.y" };
method rr() { say "method $.y"; qq() } }; my $z = X.new; $z.y = 23;
$z.rr()
<p6eval> rakudo 244d0f​: OUTPUT«method 23␤Null PMC access in
find_method('y')␤ in 'X​::qq' [...]
<szabgab> so sub() in a class does not know about the attributes of the class?
<sorear> szabgab​: subs don't have an invocant parameter
<szabgab> what is an "invocant parameter"?
<masak> szabgab​: subs "belong to the class". attributes are declared
in the class but "belong to the object". therefore, the sub can't see
the attributes.
<masak> rakudo​: class A { has $!x; sub foo { say "before"; say $!x;
say "after" }; method bar { foo } }; A.new.bar
<p6eval> rakudo 244d0f​: OUTPUT«before␤Null PMC access in
get_attr_str()␤ in 'A​::foo' [...]
* masak submits rakudobug

From @moritz

Now says

Variable $.y used where no 'self' available at line 1

which is as awesome as it gets.

Test in t/spec/S12-class/attributes.t passes.

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