print specify immutable members

generator.v

@@ -82,12 +82,17 @@ fn (mut g Generator) gen_class_print_func(stmt ClassDecl) {
     g.out.writeln('for(int i=0; i<indent + 1; i++) printf("  ");')
     g.out.write_string('printf("${member.name}: ");')
 
+
 		if member.type != 'string' && g.symbols.lookup_class(member.type) != none {
       inner_struct_name := mangle_struct(member.type)
       g.out.writeln('print_${inner_struct_name}(s.${member.name}, indent + 1);')
     } else {
       format := get_type_format(member.type)
-      g.out.write_string('printf("%${format}\\n", s.${member.name}')
+      g.out.write_string('printf("%${format}')
+			if member.is_immutable {
+  	  	g.out.write_string(' (immutable) ')
+			}
+      g.out.write_string('\\n", s.${member.name}')
 			if member.type == 'string' {
       	g.out.write_string('.string')
 			}