fix #581

irc/types.go

@@ -28,6 +28,17 @@ func (clients ClientSet) Has(client *Client) bool {
 	return ok
 }
 
+type StringSet map[string]empty
+
+func (s StringSet) Has(str string) bool {
+	_, ok := s[str]
+	return ok
+}
+
+func (s StringSet) Add(str string) {
+	s[str] = empty{}
+}
+
 // MemberSet is a set of members with modes.
 type MemberSet map[*Client]*modes.ModeSet