Start to tease apart abstract roles (the name for the whole set of po…

…ssible parameterizations) and concrete roles (a particular variant) in the type system, and tweak infix:<does> to take advantage of it. Probably more to come on this, but it's a start.

build/Makefile.in

@@ -91,6 +91,7 @@ BUILTINS_PIR = \
   src/metamodel/GrammarHOW.pir \
   src/builtins/Any.pir \
   src/builtins/Role.pir \
+  src/builtins/ConcreteRole.pir \
   src/builtins/Abstraction.pir \
   src/builtins/Positional.pir \
   src/builtins/Iterable.pir \

src/builtins/ConcreteRole.pir

@@ -0,0 +1,41 @@
+## $Id$
+
+=head1 NAME
+
+src/classes/ConcreteRole.pir - methods for the ConcreteRole class
+
+=head1 Description
+
+A concrete role is a role that has been selected from an abstract role by
+providing a (possibly empty) set of role parameters. This class for now
+is primarily just designed to know how to match one of them in a multiple
+dispatch.
+
+=head1 Methods
+
+=over 4
+
+=cut
+
+.namespace ['ConcreteRole']
+
+.sub 'onload' :anon :init :load
+    .local pmc p6meta, proto
+    p6meta = get_hll_global ['Mu'], '$!P6META'
+    proto = p6meta.'new_class'('ConcreteRole', 'parent'=>'Any')
+.end
+
+.sub 'PROTOOVERRIDES' :method
+    .return ('new', 'ACCEPTS')
+.end
+
+.sub 'ACCEPTS' :method
+    .param pmc topic
+    $I0 = isa topic, 'P6role'
+    $P0 = '&prefix:<?>'($I0)
+    .return ($P0)
+.end
+
+=back
+
+=cut

src/core/operators.pm

@@ -93,8 +93,11 @@ our sub undefine(Mu \$x) {
 }
 
 our multi infix:<does>(Mu \$do-it-to-me, Role $r) {
-    my $specific_role = $r!select;
-    my $applicator    = $specific_role.^applier_for($do-it-to-me);
+    &infix:<does>($do-it-to-me, $r!select)
+}
+
+our multi infix:<does>(Mu \$do-it-to-me, ConcreteRole $r) {
+    my $applicator = $r.^applier_for($do-it-to-me);
     $applicator.apply($do-it-to-me, [$r]);
     $do-it-to-me
 }