{"action":"opened","issue":{"url":"https://api.github.com/repos/elm-lang/elm-compiler/issues/1110","labels_url":"https://api.github.com/repos/elm-lang/elm-compiler/issues/1110/labels{/name}","comments_url":"https://api.github.com/repos/elm-lang/elm-compiler/issues/1110/comments","events_url":"https://api.github.com/repos/elm-lang/elm-compiler/issues/1110/events","html_url":"https://github.com/elm-lang/elm-compiler/issues/1110","id":111884428,"number":1110,"title":"Type checker should forbid unbound type variables in type aliases","user":{"login":"psfblair","id":176193,"avatar_url":"https://avatars.githubusercontent.com/u/176193?v=3","gravatar_id":"","url":"https://api.github.com/users/psfblair","html_url":"https://github.com/psfblair","followers_url":"https://api.github.com/users/psfblair/followers","following_url":"https://api.github.com/users/psfblair/following{/other_user}","gists_url":"https://api.github.com/users/psfblair/gists{/gist_id}","starred_url":"https://api.github.com/users/psfblair/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/psfblair/subscriptions","organizations_url":"https://api.github.com/users/psfblair/orgs","repos_url":"https://api.github.com/users/psfblair/repos","events_url":"https://api.github.com/users/psfblair/events{/privacy}","received_events_url":"https://api.github.com/users/psfblair/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":0,"created_at":"2015-10-16T18:23:41Z","updated_at":"2015-10-16T18:23:41Z","closed_at":null,"body":"Example case:\r\n\r\n    type MyData = MyData String\r\n    type alias MyDataAlias a = MyData\r\n\r\nComplete example here: http://share-elm.com/sprout/56213fb6e4b0966c193dd8ee\r\n\r\nThe type checker just ignores the type variable, but this should probably be an error instead -- either the author intended a phantom type, which can't be introduced by a type alias, or intended to bind the type variable, in which case the code is erroneous. I suggest having the type checker say something like: \"You have an unbound type variable in a type alias. Phantom types are not supported through aliases. Maybe you meant ...?\"\r\n\r\n\r\n"}}