{"action":"created","issue":{"url":"https://api.github.com/repos/google/closure-compiler/issues/1529","repository_url":"https://api.github.com/repos/google/closure-compiler","labels_url":"https://api.github.com/repos/google/closure-compiler/issues/1529/labels{/name}","comments_url":"https://api.github.com/repos/google/closure-compiler/issues/1529/comments","events_url":"https://api.github.com/repos/google/closure-compiler/issues/1529/events","html_url":"https://github.com/google/closure-compiler/issues/1529","id":133295759,"number":1529,"title":"Extern for `Array.from` makes optional argument required and nullable","user":{"login":"mgiuffrida","id":1449368,"avatar_url":"https://avatars.githubusercontent.com/u/1449368?v=3","gravatar_id":"","url":"https://api.github.com/users/mgiuffrida","html_url":"https://github.com/mgiuffrida","followers_url":"https://api.github.com/users/mgiuffrida/followers","following_url":"https://api.github.com/users/mgiuffrida/following{/other_user}","gists_url":"https://api.github.com/users/mgiuffrida/gists{/gist_id}","starred_url":"https://api.github.com/users/mgiuffrida/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/mgiuffrida/subscriptions","organizations_url":"https://api.github.com/users/mgiuffrida/orgs","repos_url":"https://api.github.com/users/mgiuffrida/repos","events_url":"https://api.github.com/users/mgiuffrida/events{/privacy}","received_events_url":"https://api.github.com/users/mgiuffrida/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":1,"created_at":"2016-02-12T17:16:03Z","updated_at":"2016-02-12T17:21:29Z","closed_at":null,"body":"The extern added in #1377 incorrectly makes the 2nd param required & nullable, even though it is named `opt_mapFn` and [according to MDN is optional](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/from) but cannot be null.\r\n\r\n```\r\n + * @param {string|!Array<T>|!IArrayLike<T>|!Iterable<T>} arrayLike\r\n + * @param {?function(this:S, string|T, number,\r\n + *     string|!Array<T>|!IArrayLike<T>|!Iterable<T>): R} opt_mapFn\r\n + * @param {S=} opt_this\r\n```\r\n\r\nThe `?` should instead be a `=`. The function can be undefined but not null."},"comment":{"url":"https://api.github.com/repos/google/closure-compiler/issues/comments/183419477","html_url":"https://github.com/google/closure-compiler/issues/1529#issuecomment-183419477","issue_url":"https://api.github.com/repos/google/closure-compiler/issues/1529","id":183419477,"user":{"login":"MatrixFrog","id":244381,"avatar_url":"https://avatars.githubusercontent.com/u/244381?v=3","gravatar_id":"","url":"https://api.github.com/users/MatrixFrog","html_url":"https://github.com/MatrixFrog","followers_url":"https://api.github.com/users/MatrixFrog/followers","following_url":"https://api.github.com/users/MatrixFrog/following{/other_user}","gists_url":"https://api.github.com/users/MatrixFrog/gists{/gist_id}","starred_url":"https://api.github.com/users/MatrixFrog/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/MatrixFrog/subscriptions","organizations_url":"https://api.github.com/users/MatrixFrog/orgs","repos_url":"https://api.github.com/users/MatrixFrog/repos","events_url":"https://api.github.com/users/MatrixFrog/events{/privacy}","received_events_url":"https://api.github.com/users/MatrixFrog/received_events","type":"User","site_admin":false},"created_at":"2016-02-12T17:21:29Z","updated_at":"2016-02-12T17:21:29Z","body":"Aha good catch. This will be easier to fix internally since there is a chance it could break some projects."}}