# New Ticket Created by "Carl Mäsak"
# Please include the string: [perl #124226]
# in the subject line of all future correspondence about this issue.
# <URL: https://rt.perl.org/Ticket/Display.html?id=124226 >
<[Tux]> m: class C { has Int $!x; method foo { ($!x, my $b) = (1,2);}};C.foo
19:45 <+camelia> rakudo-moar 6caf1d: OUTPUT«Cannot look up attributes
in a type object in method foo [...]
<[Tux]> is that explainable?
<masak> you're calling C.foo, the .foo method on the type object C
<masak> the type object doesn't really properly have an $!x
<masak> m: class C { has Int $!x; method foo { ($!x, my $b) =
(1,2);}}; C.new.foo
<camelia> rakudo-moar 6caf1d: ( no output )
<masak> that works.
<TimToady> "Cannot look up attributes in a type object" is an
implementor-centric error message, not a user-centric one
<Juerd> TimToady: "Instance attribute used in non-instance method call"? :)
<masak> TimToady: actually, that error message could fail statically
in this case.
<masak> since C is already resolved at compile time.
<masak> no need to make it survive until runtime and then fail.
[...]
<masak> no-one else liked the idea of statically erroring out with
"call will never work" for the C.foo case where C is already
statically resolved?
<nine_> masak: I do
<Juerd> masak: Could work, but can't methods be marked as instance-only?
<nine_> masak: the earlier errors are reported the better
<PerlJam> masak: How does the compiler decide that it will never work? and when?
<Juerd> Because then, any use of $!foo could simply mark the method as
instance-only
<Juerd> And the error message could be simpler.
<Juerd> "Method foo can only be called on an instance of C, not on C itself."
<PerlJam> (compiler hints)++ if we can reasonably have them.
<PerlJam> I guess, if you declare the sig right, all the info is easy
to get at. But without that, it seems like a bit of guessing for the
compiler to do it.
<masak> PerlJam: compiler sees the call C.foo, and has already set a
flag that the foo method in class C accesses an attribute. boom.
* masak submits rakudobug
<Juerd> "Method foo can only be called on an instance of C, not on C
itself, because C.foo accesses instance attribute $!x."
<masak> neat. +1
<PerlJam> masak: flagging methods like that seems like quite a bit of
bookkeeping for marginal benefit.
<masak> really? seems worth it to me...
<masak> it's a small hash somewhere in the compiler.
<masak> %accattr<C.foo> = True;
<Juerd> It could be a boolean flag (instance-only) and an array of
further explanations
<[Coke]> masak: I think you mean a compile-time static check, not a
static static check. ;)
<masak> [Coke]: yes. thank you. I meant... that, what you said.
