One would expect an error message such as:
$ 6 'role R[$a,$b] {}; class C does R[1] {}'
===SORRY!===
No appropriate parametric role variant available for ‘R'
but even that message is rather LTA, as it doesn’t mention which parameters
were tried and which candidates are available.
Liz
====================
> On 05 Sep 2015, at 12:38, dakkar (via RT) <perl6-bugs-follo...@perl.org>
> wrote:
>
> # New Ticket Created by dakkar
> # Please include the string: [perl #125996]
> # in the subject line of all future correspondence about this issue.
> # <URL: https://rt.perl.org/Ticket/Display.html?id=125996 >
>
>
> This code::
>
> role R[$a,$b] {}
> role R2[$x] does R[1] {}
> class C does R2[1] {}
>
> C.new;
>
> Produces the error message::
>
> ===SORRY!===
> Cannot find method 'collisions'
>
> The error happens in ``RoleToClassApplier::apply``: something goes
> wrong with the nested role specialisation, and the compiler tries to
> apply a ``NQPMu``.
>
> --
> Dakkar - <Mobilis in mobile>
> GPG public key fingerprint = A071 E618 DD2C 5901 9574
> 6FE2 40EA 9883 7519 3F88
> key id = 0x75193F88
>
> Giving up on assembly language was the apple in our Garden of Eden:
> Languages whose use squanders machine cycles are sinful. The LISP
> machine now permits LISP programmers to abandon bra and fig-leaf.
> -- Epigrams in Programming, ACM SIGPLAN Sept. 1982
