doc private attributes

Author: gfldex

doc/Language/typesystem.pod6

@@ -24,6 +24,21 @@ TODO
 
 TODO
 
+=head3 Attributes
+
+=head4 Private Attributes
+
+Private attributes do not have public accessor methods generated automatically.
+As such they can not be altered from outside the class they are defined in.
+
+    class C {
+        has $!priv;
+        submethod BUILD { $!priv = 42 }
+    };
+
+    say (.name, .package, .has_accessor) for C.new.^attributes;
+    # OUTPUT«($!priv (C) False)␤»
+
 =head3 Methods
 
 =head4 Fallback method