{"action":"created","issue":{"url":"https://api.github.com/repos/ocsigen/tyxml/issues/108","repository_url":"https://api.github.com/repos/ocsigen/tyxml","labels_url":"https://api.github.com/repos/ocsigen/tyxml/issues/108/labels{/name}","comments_url":"https://api.github.com/repos/ocsigen/tyxml/issues/108/comments","events_url":"https://api.github.com/repos/ocsigen/tyxml/issues/108/events","html_url":"https://github.com/ocsigen/tyxml/issues/108","id":145401611,"number":108,"title":"Covariance issues with wrapping","user":{"login":"Drup","id":801124,"avatar_url":"https://avatars.githubusercontent.com/u/801124?v=3","gravatar_id":"","url":"https://api.github.com/users/Drup","html_url":"https://github.com/Drup","followers_url":"https://api.github.com/users/Drup/followers","following_url":"https://api.github.com/users/Drup/following{/other_user}","gists_url":"https://api.github.com/users/Drup/gists{/gist_id}","starred_url":"https://api.github.com/users/Drup/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/Drup/subscriptions","organizations_url":"https://api.github.com/users/Drup/orgs","repos_url":"https://api.github.com/users/Drup/repos","events_url":"https://api.github.com/users/Drup/events{/privacy}","received_events_url":"https://api.github.com/users/Drup/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":1,"created_at":"2016-04-02T18:36:36Z","updated_at":"2016-04-02T18:37:19Z","closed_at":null,"body":"While working with the ppx, I noticed something ... strange.\r\n\r\n```\r\n# let x = Html5.Xml.W.nil () ;;\r\nval x : '_a list = []  \r\nlet x : _ list = Html5.Xml.W.nil () ;;\r\nval x : 'a list = []  \r\n```\r\n\r\nApparently, the functor stack hides the covariance, since `Xml_wrap.S.tlist` is not marked covariant. \r\n@vasilisp Do you think we could turn it covariant ? Are all the wrapper we have covariants ? Given the heavy use of subtyping, It would seems natural to enforce that."},"comment":{"url":"https://api.github.com/repos/ocsigen/tyxml/issues/comments/204770958","html_url":"https://github.com/ocsigen/tyxml/issues/108#issuecomment-204770958","issue_url":"https://api.github.com/repos/ocsigen/tyxml/issues/108","id":204770958,"user":{"login":"Drup","id":801124,"avatar_url":"https://avatars.githubusercontent.com/u/801124?v=3","gravatar_id":"","url":"https://api.github.com/users/Drup","html_url":"https://github.com/Drup","followers_url":"https://api.github.com/users/Drup/followers","following_url":"https://api.github.com/users/Drup/following{/other_user}","gists_url":"https://api.github.com/users/Drup/gists{/gist_id}","starred_url":"https://api.github.com/users/Drup/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/Drup/subscriptions","organizations_url":"https://api.github.com/users/Drup/orgs","repos_url":"https://api.github.com/users/Drup/repos","events_url":"https://api.github.com/users/Drup/events{/privacy}","received_events_url":"https://api.github.com/users/Drup/received_events","type":"User","site_admin":false},"created_at":"2016-04-02T18:37:19Z","updated_at":"2016-04-02T18:37:19Z","body":"As a limited fix, only for the native tyxml implementation, I did https://github.com/ocsigen/tyxml/pull/107/commits/85c62cdcdd2448743aa481bbde9f8929a2002781"}}