On Mon, 04 Jun 2018 07:31:40 -0700, richard.hogab...@gmail.com wrote:
> 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.
>
Thanks for the report, but there's no bug here.
The `has $.foo` attribute syntax is just a shorthand for writing `has $!foo;
method foo { $!foo }`.
In other words, the compiler auto-generated an accessor method for you.
When you use `$.foo` syntax inside a method, it's a shorthand for `self.foo`;
in other words, it's a
method call.
If you define a method with the same name as the attribute, then it signals to
the compiler that you chose
to take care of accessor method yourself.
Also, to return a writeable container, you need to either use `return-rw`
instead of plain `return` when
using explicit return, or apply the `is rw` trait to the method, when using
implicit return:
method var1() is rw { return $!var }
method var2() { return-rw $!var }
With that knowledge, you can see why the failing examples fail:
* EXAMPLE 3: You defined a method with the same name as attribute, so it'll
function as the accessor. The body
of that method is empty, so it returns `Nil` and hence the error
about trying to assign to `Nil`
* EXAMPLE 4: Again, you defined your own accessor, but now you're also using
`$.var` syntax inside, so the method
infiniloops calling itself over and over. Hence the hang.
* EXAMPLE 5: You've used `return` instead of `return-rw`, so only a readonly
value is returned instead of a
writable container. Hence the error
> but shouldn't there be some type of prohibition/warning?
No, as it's perfectly fine to declare your own accessors. Of course, writing
`has $.foo` instead of `has $!foo` is
pointless, in that case, but it serves as a hint to the programmer that it's a
public attribute, so I don't think
warning about that is appropriate.
