tell that BUILD don't got access to public accessors

Author: gfldex

doc/Language/typesystem.pod6

@@ -84,7 +84,9 @@ The submethod C<BUILD> is called by C<.BUILDALL> defined in L</type/Mu>, which
 in turn is called by L<.bless|/type/Mu#method_bless>. It is meant to set
 private and public attributes of a class and receives all names attributes
 passed into C<.bless>. Since it is called by C<BUILDALL> it is called by the
-default constructor L<.new|/type/Mu#method_new> defined in C<Mu>.
+default constructor L<.new|/type/Mu#method_new> defined in C<Mu>. Public
+accessor methods are not available in C<BUILD> use private attribute notation
+instead.
 
     class C {
         has $.attr;