LTA: roles enforce method signatures only with multi methods

[zoffixznet]

From https://stackoverflow.com/questions/52861619/are-typed-signatures-for-stubbed-methods-not-enforced-in-roles-for-perl6

Looks like only methods don't care if signatures match:

$ perl6 -e 'role Foo { method bar (Int) { … } }; class Bar does Foo { method bar(Str) { } }'
$

Yet, the functionality of enforcing correct signatures is available if you swap to using multi methods:

$ perl6 -e 'role Foo { multi method bar (Int) { … } }; class Bar does Foo { multi method bar(Str) { } }'
===SORRY!=== Error while compiling -e
Multi method 'bar' with signature :(Bar: Int $, *%_) must be implemented by Bar because it is required by a role
at -e:1

$ perl6 -v
This is Rakudo version 2018.06-146-g1b3dd35 built on MoarVM version 2018.06-141-gcae4731
implementing Perl 6.c.

IMO, only methods should enforce signatures too.

[jnthn]

Seems like a reasonable thing for the 6.e wish list (I think it'll be too much of a breaking change to do it without a language version change).