Implement accessor attribute for Attribute descriptor class.

src/parrot/ClassHOW.pir

@@ -82,16 +82,31 @@ Attribute descriptors.
     unless attr_it goto attr_it_loop_end
     $S0 = shift attr_it
     cur_attr_hash = attributes[$S0]
+
+    # Name
     $S0 = cur_attr_hash['name']
+
+    # Type
     $P0 = cur_attr_hash['type']
     unless null $P0 goto type_done
     $P0 = get_root_global [.RAKUDO_HLL], 'Object'
   type_done:
+
+    # Build
     $P1 = cur_attr_hash['init_value']
     unless null $P1 goto build_done
     $P1 = root_new [.RAKUDO_HLL; 'Failure']
   build_done:
-    cur_attr_info = attr_proto.'new'('name' => $S0, 'type' => $P0, 'build' => $P1)
+
+    # Accessor
+    $P2 = cur_attr_hash['accessor']
+    unless null $P2 goto accessor_done
+    $P2 = box 0
+  accessor_done:
+    $P3 = get_root_global [.RAKUDO_HLL], 'prefix:?'
+    $P2 = $P3($P2)
+
+    cur_attr_info = attr_proto.'new'('name' => $S0, 'type' => $P0, 'build' => $P1, 'accessor' => $P2)
     result_list.'push'(cur_attr_info)
     goto attr_it_loop
   attr_it_loop_end:

src/parser/actions.pm

@@ -1737,6 +1737,9 @@ method scope_declarator($/) {
                         $init_value.named('init_value');
                         $has.push($init_value);
                     }
+                    if $var<twigil> eq '.' {
+                        $has.push(PAST::Val.new( :value(1), :named('accessor') ));
+                    }
                     if $var<traitlist> {
                         # If we have a handles, then we pass that specially.
                         my $handles := has_compiler_trait($var<traitlist>, 'trait_mod:handles');

src/setting/Attribute.pm

@@ -2,6 +2,7 @@ class Attribute {
     has $.name;
     has $.type;
     has $.build;
+    has $.accessor;
 }
 
 # vim: ft=perl6