#282优化，切换主邮箱时检查是否被别的用户使用了。

models/user_mail.go

@@ -293,6 +293,16 @@ func MakeEmailPrimary(email *EmailAddress) error {
 	}
 
 	user.Email = email.Email
+
+	has, err = sess.Where("id!=?", user.ID).
+		And("type=?", user.Type).
+		And("email=?", strings.ToLower(user.Email)).
+		Get(new(User))
+	if err != nil {
+		return err
+	} else if has {
+		return ErrEmailAlreadyUsed{user.Email}
+	}
 	if _, err = sess.ID(user.ID).Cols("email").Update(user); err != nil {
 		return err
 	}