From @jdv

See https://gist.github.com/anonymous/1bac642c0a774065bb087dab4e03c694.

Note that the point of using the private method was because the attr is
private in the real code.

Can't repro if​:
* switch the "for (​:k1<v1>)" to "for (1..1)"
* change the foo method to public
* have only one class
* move send-and-store into the classes

From @zoffixznet

Attached is the OP's gist, in case that URL ever stops working...

From @zoffixznet

[jdv@​new-host-2 p6-agent]$ cat t/99-test.t
use v6;

role Agent {
  has Str $.id is required;
  has $.state = {};

  method !foo { $!state }
}

role Agent​::WebSourceAgent {
  method send-and-store { for (​:k1<v1>) { if self!foo { } } }
}

class Agent​::AtomAgent does Agent does Agent​::WebSourceAgent {
  method run { loop { self.send-and-store } }
}

class Agent​::FeedBurnerAgent does Agent does Agent​::WebSourceAgent {
  method run { loop { self.send-and-store } }
}

await map { start {
  CATCH { default { die "E​:{$_.gist}​:E"; exit; } };
  $_ mod 2
  ?? Agent​::AtomAgent.new(​:id("a-$_")).run
  !! Agent​::FeedBurnerAgent.new(​:id("f-$_")).run;
} }, 1..50;

# vim​:ft=perl6
[jdv@​new-host-2 p6-agent]$ time perl6 t/99-test.t
Tried to get the result of a broken Promise
  in block <unit> at t/99-test.t line 22

Original exception​:
  E​:P6opaque​: no such attribute '$!state' in type Agent​::FeedBurnerAgent when trying to get a value
  in method foo at t/99-test.t line 7
  in method send-and-store at t/99-test.t line 11
  in method run at t/99-test.t line 15
  in block at t/99-test.t line 24
  :E
  in block at t/99-test.t line 23
  in method send-and-store at t/99-test.t line 11
  in method run at t/99-test.t line 15
  in block at t/99-test.t line 24

real 0m0.541s
user 0m0.974s
sys 0m0.068s
[jdv@​new-host-2 p6-agent]$ time perl6 t/99-test.t
^C

real 1m13.959s
user 4m51.781s
sys 0m0.195s
[jdv@​new-host-2 p6-agent]$ time perl6 t/99-test.t
^C

real 0m22.663s
user 1m27.439s
sys 0m0.459s
[jdv@​new-host-2 p6-agent]$ time perl6 t/99-test.t
Tried to get the result of a broken Promise
  in block <unit> at t/99-test.t line 22

Original exception​:
  E​:P6opaque​: no such attribute '$!state' in type Agent​::FeedBurnerAgent when trying to get a value
  in method foo at t/99-test.t line 7
  in method send-and-store at t/99-test.t line 11
  in method run at t/99-test.t line 15
  in block at t/99-test.t line 24
  :E
  in block at t/99-test.t line 23
  in method send-and-store at t/99-test.t line 11
  in method run at t/99-test.t line 15
  in block at t/99-test.t line 24

real 0m0.756s
user 0m1.280s
sys 0m0.110s
[jdv@​new-host-2 p6-agent]$ time perl6 t/99-test.t
^C

real 0m19.591s
user 1m15.996s
sys 0m0.464s
[jdv@​new-host-2 p6-agent]$ time perl6 t/99-test.t
Use of uninitialized value $s of type Any in string context.
Methods .^name, .perl, .gist, or .say can be used to stringify it to something meaningful.
  in block at t/99-test.t line 23
Tried to get the result of a broken Promise
  in block <unit> at t/99-test.t line 22

Original exception​:
  E​:P6opaque​: no such attribute '$!state' in type Agent​::FeedBurnerAgent when trying to get a value
  in method foo at t/99-test.t line 7
  in method send-and-store at t/99-test.t line 11
  in method run at t/99-test.t line 15
  in block at t/99-test.t line 24
  :E
  in block at t/99-test.t line 23
  in method send-and-store at t/99-test.t line 11
  in method run at t/99-test.t line 15
  in block at t/99-test.t line 24

real 0m0.692s
user 0m1.159s
sys 0m0.091s
[jdv@​new-host-2 p6-agent]$ time perl6 t/99-test.t
Tried to get the result of a broken Promise
  in block <unit> at t/99-test.t line 22

Original exception​:
  E​:P6opaque​: no such attribute '$!state' in type Agent​::FeedBurnerAgent when trying to get a value
  in method foo at t/99-test.t line 7
  in method send-and-store at t/99-test.t line 11
  in method run at t/99-test.t line 15
  in block at t/99-test.t line 24
  :E
  in block at t/99-test.t line 23
  in method send-and-store at t/99-test.t line 11
  in method run at t/99-test.t line 15
  in block at t/99-test.t line 24

real 0m0.512s
user 0m0.854s
sys 0m0.081s
[jdv@​new-host-2 ~]$ perl6 -v
This is Rakudo version 2016.12-377-g7ddc5f7 built on MoarVM version 2016.12-113-gd1da1ba
implementing Perl 6.c.
[jdv@​new-host-2 ~]$

From @jdv

Note that running under MVM_SPESH_DISABLE=1 seems to elide the bug.

On 2017.02.01 01​:01 pm, perl6 via RT wrote​:

Greetings,

This message has been automatically generated in response to the
creation of a trouble ticket regarding​:
"[BUG] [CONC] attribute from one role used in another via private
method gone missing",
a summary of which appears below.

There is no need to reply to this message right now. Your ticket has
been
assigned an ID of [perl #​130690].

Please include the string​:

     \[perl #​130690\]

in the subject line of all future correspondence about this issue. To
do so,
you may reply to this message.

                    Thank you,
                    perl6\-bugs\-followup@​perl\.org

-------------------------------------------------------------------------
See
https://gist.github.com/anonymous/1bac642c0a774065bb087dab4e03c694.

Note that the point of using the private method was because the attr
is
private in the real code.

Can't repro if​:
* switch the "for (​:k1<v1>)" to "for (1..1)"
* change the foo method to public
* have only one class
* move send-and-store into the classes