document set_rw

Author: moritz

lib/Type/Metamodel/AttributeContainer.pod

@@ -26,9 +26,27 @@ It can for example be of L<type Attribute|/type/Attribute>.
 Returns a list of attributes. For most Perl 6 types, these will be objects of
 L<type Attribute|/type/Attribute>.
 
+=head2 method set_rw
+
+    method set_rw(Metamodel::AttributeContainer: $obj)
+
+Marks a type whose attributes default to having a write accessor. For example
+in
+
+    class Point is rw {
+        has $.x;
+        has $.y;
+    }
+
+The C<is rw> trait on the class calls the C<set_rw> method on the meta class,
+making all the attributes implicitly writable, so that you can write;
+
+    my $p = Point.new(x => 1, y => 2);
+    $p.x = 42;
+
 =begin comment
 
-TODO: compose_attributes, set_rw, rw, get_attribute_for_usage
+TODO: compose_attributes, rw, get_attribute_for_usage
 
 Also TODO: desribe :local, :excl, :all options of method attributes