{"action":"created","issue":{"url":"https://api.github.com/repos/apple/swift/issues/12029","repository_url":"https://api.github.com/repos/apple/swift","labels_url":"https://api.github.com/repos/apple/swift/issues/12029/labels{/name}","comments_url":"https://api.github.com/repos/apple/swift/issues/12029/comments","events_url":"https://api.github.com/repos/apple/swift/issues/12029/events","html_url":"https://github.com/apple/swift/pull/12029","id":259337243,"number":12029,"title":"[DO NOT MERGE][stdlib] Constrain Sequence methods that return AnySequence","user":{"login":"airspeedswift","id":8058277,"avatar_url":"https://avatars1.githubusercontent.com/u/8058277?v=4","gravatar_id":"","url":"https://api.github.com/users/airspeedswift","html_url":"https://github.com/airspeedswift","followers_url":"https://api.github.com/users/airspeedswift/followers","following_url":"https://api.github.com/users/airspeedswift/following{/other_user}","gists_url":"https://api.github.com/users/airspeedswift/gists{/gist_id}","starred_url":"https://api.github.com/users/airspeedswift/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/airspeedswift/subscriptions","organizations_url":"https://api.github.com/users/airspeedswift/orgs","repos_url":"https://api.github.com/users/airspeedswift/repos","events_url":"https://api.github.com/users/airspeedswift/events{/privacy}","received_events_url":"https://api.github.com/users/airspeedswift/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":17,"created_at":"2017-09-21T00:00:59Z","updated_at":"2017-10-02T21:25:37Z","closed_at":null,"author_association":"MEMBER","pull_request":{"url":"https://api.github.com/repos/apple/swift/pulls/12029","html_url":"https://github.com/apple/swift/pull/12029","diff_url":"https://github.com/apple/swift/pull/12029.diff","patch_url":"https://github.com/apple/swift/pull/12029.patch"},"body":"Currently `Sequence`'s default `SubSequence` is `AnySequence`, but it gets it in a roundabout way. This does it more explicitly, and then constrains the default implementations to sequences that don't have a custom subsequence (including collections, which do this via slicing instead). \r\n\r\nThis means you no longer get a bunch of confusing overloads on collections like `Array`:\r\n\r\n```swift\r\nlet a = [1,2,3]\r\n// compiles as of 4.0 but shouldn't\r\nlet s: AnySequence<Int> = a.dropFirst(1)\r\n```\r\n\r\nBuilt on top of #11923, for which I pine. It might not need it.\r\n"},"comment":{"url":"https://api.github.com/repos/apple/swift/issues/comments/333669987","html_url":"https://github.com/apple/swift/pull/12029#issuecomment-333669987","issue_url":"https://api.github.com/repos/apple/swift/issues/12029","id":333669987,"user":{"login":"swift-ci","id":15467072,"avatar_url":"https://avatars0.githubusercontent.com/u/15467072?v=4","gravatar_id":"","url":"https://api.github.com/users/swift-ci","html_url":"https://github.com/swift-ci","followers_url":"https://api.github.com/users/swift-ci/followers","following_url":"https://api.github.com/users/swift-ci/following{/other_user}","gists_url":"https://api.github.com/users/swift-ci/gists{/gist_id}","starred_url":"https://api.github.com/users/swift-ci/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/swift-ci/subscriptions","organizations_url":"https://api.github.com/users/swift-ci/orgs","repos_url":"https://api.github.com/users/swift-ci/repos","events_url":"https://api.github.com/users/swift-ci/events{/privacy}","received_events_url":"https://api.github.com/users/swift-ci/received_events","type":"User","site_admin":false},"created_at":"2017-10-02T21:25:37Z","updated_at":"2017-10-02T21:25:37Z","author_association":"CONTRIBUTOR","body":"**Build failed**\n[Swift Test Linux Platform](https://ci.swift.org/job/swift-PR-Linux/683/)\nGit Sha - bf5c960e4690ecca16213477494db883cc2ca43b\n"}}
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