From @TimToady

21​:25 < TimToady> m​: say Iterable === Any
21​:25 <+camelia> rakudo-moar 2ad739​: OUTPUT«Method 'iterator' must be
implemented by Iterable because it is required by a role␤ in any
  compose_method_table at gen/moar/m-Metamodel.nqp​:2661␤ in
any apply at gen/moar/m-Metamodel.nqp​:2671␤ in any compose at
  gen/moar/m-Metamodel.nqp​:2807␤ in…»
21​:49 < TimToady> m​: sub foo(Iterable $s) {...}; say &foo.signature
21​:49 <+camelia> rakudo-moar 2ad739​: OUTPUT«Method 'iterator' must be
implemented by Iterable because it is required by a role␤ in any
  compose_method_table at gen/moar/m-Metamodel.nqp​:2661␤ in
any apply at gen/moar/m-Metamodel.nqp​:2671␤ in any compose at
  gen/moar/m-Metamodel.nqp​:2807␤ in…»
21​:50 < TimToady> that tries to call Iterable.WHICH, and that forces role
punning, which doesn't work here
21​:50 < TimToady> m​: say Iterable.foo
21​:50 <+camelia> rakudo-moar 2ad739​: OUTPUT«Method 'iterator' must be
implemented by Iterable because it is required by a role␤ in any
  compose_method_table at gen/moar/m-Metamodel.nqp​:2661␤ in
any apply at gen/moar/m-Metamodel.nqp​:2671␤ in any compose at
  gen/moar/m-Metamodel.nqp​:2807␤ in…»
21​:50 < TimToady> doesn't matter which method you call on it

From @jnthn

On Mon Nov 09 22​:21​:58 2015, larry wrote​:

21​:25 < TimToady> m​: say Iterable === Any
21​:25 <+camelia> rakudo-moar 2ad739​: OUTPUT«Method 'iterator' must be
implemented by Iterable because it is required by a role␤ in any
compose_method_table at gen/moar/m-Metamodel.nqp​:2661␤ in
any apply at gen/moar/m-Metamodel.nqp​:2671␤ in any compose at
gen/moar/m-Metamodel.nqp​:2807␤ in…»
21​:49 < TimToady> m​: sub foo(Iterable $s) {...}; say &foo.signature
21​:49 <+camelia> rakudo-moar 2ad739​: OUTPUT«Method 'iterator' must be
implemented by Iterable because it is required by a role␤ in any
compose_method_table at gen/moar/m-Metamodel.nqp​:2661␤ in
any apply at gen/moar/m-Metamodel.nqp​:2671␤ in any compose at
gen/moar/m-Metamodel.nqp​:2807␤ in…»
21​:50 < TimToady> that tries to call Iterable.WHICH, and that forces role
punning, which doesn't work here
21​:50 < TimToady> m​: say Iterable.foo
21​:50 <+camelia> rakudo-moar 2ad739​: OUTPUT«Method 'iterator' must be
implemented by Iterable because it is required by a role␤ in any
compose_method_table at gen/moar/m-Metamodel.nqp​:2661␤ in
any apply at gen/moar/m-Metamodel.nqp​:2671␤ in any compose at
gen/moar/m-Metamodel.nqp​:2807␤ in…»
21​:50 < TimToady> doesn't matter which method you call on it

Well, trying to pun the role is the correct behavior on method calls on it, in general. We maintained a rather short list of methods that did not trigger punning; I've just expanded it quite a bit to include things people are likely to not want it to pun on, including .WHICH. The behavior for calling .foo is correct​: it should try to pun and fail due to the missing method.

Tests in S14-roles/stubs.t.

The RT System itself - Status changed from 'new' to 'open'

@jnthn - Status changed from 'open' to 'resolved'