Merge globals bug in rakudo

Bar.pm

module Bar;

multi trait_mod:<is>(Routine $r, :$bar!) is export { }

Foo.pm

module Foo;

multi trait_mod:<is>(Routine $r, :$foo!) is export { }

test_nok.pl

use Foo;
use Bar;

sub a is foo { };

test_ok.pl

use Foo;
sub a is foo { };

Merging global symbols does not work for multi trait_mods.

So if you try to import two trait_mods with different signatures, the program dies rather than add the signatures to the dispatcher list.

First step is to comment out the line 269 in rakudo/src/Perl6/World.pm:

# XXX TODO: Merge handling.
nqp::push(@clash, $_.key);

After that your test script wont die anymore, but you get the trait_mods from perl core and the module you importet last. But you obviously should get the trait_mods from core and both modules.