{"action":"created","comment":{"url":"https://api.github.com/repos/Microsoft/TypeScript/pulls/comments/38542808","id":38542808,"diff_hunk":"@@ -7039,12 +7041,28 @@ namespace ts {\n                 hasSpreadElement = hasSpreadElement || e.kind === SyntaxKind.SpreadElementExpression;\r\n             }\r\n             if (!hasSpreadElement) {\r\n+                // If array literal is actually a destructuring pattern, mark it as an implied type. We do this such\r\n+                // that we get the same behavior for \"var [x, y] = []\" and \"[x, y] = []\".\r\n+                if (inDestructuringPattern && elementTypes.length) {\r\n+                    return createImpliedType(createTupleType(elementTypes));\r","path":"src/compiler/checker.ts","position":56,"original_position":56,"commit_id":"66e3abaa12c8fab57d99c77807341f553907a7f5","original_commit_id":"66e3abaa12c8fab57d99c77807341f553907a7f5","user":{"login":"ahejlsberg","id":4226954,"avatar_url":"https://avatars.githubusercontent.com/u/4226954?v=3","gravatar_id":"","url":"https://api.github.com/users/ahejlsberg","html_url":"https://github.com/ahejlsberg","followers_url":"https://api.github.com/users/ahejlsberg/followers","following_url":"https://api.github.com/users/ahejlsberg/following{/other_user}","gists_url":"https://api.github.com/users/ahejlsberg/gists{/gist_id}","starred_url":"https://api.github.com/users/ahejlsberg/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/ahejlsberg/subscriptions","organizations_url":"https://api.github.com/users/ahejlsberg/orgs","repos_url":"https://api.github.com/users/ahejlsberg/repos","events_url":"https://api.github.com/users/ahejlsberg/events{/privacy}","received_events_url":"https://api.github.com/users/ahejlsberg/received_events","type":"User","site_admin":false},"body":"If we want to allow `var { x, y } = {}` and the corresponding assignment `{ x, y } = {}` then we'd have to do it for object literals as well.","created_at":"2015-09-02T15:05:49Z","updated_at":"2015-09-02T15:05:49Z","html_url":"https://github.com/Microsoft/TypeScript/pull/4598#discussion_r38542808","pull_request_url":"https://api.github.com/repos/Microsoft/TypeScript/pulls/4598","_links":{"self":{"href":"https://api.github.com/repos/Microsoft/TypeScript/pulls/comments/38542808"},"html":{"href":"https://github.com/Microsoft/TypeScript/pull/4598#discussion_r38542808"},"pull_request":{"href":"https://api.github.com/repos/Microsoft/TypeScript/pulls/4598"}}},"pull_request":{"url":"https://api.github.com/repos/Microsoft/TypeScript/pulls/4598","id":43923717,"html_url":"https://github.com/Microsoft/TypeScript/pull/4598","diff_url":"https://github.com/Microsoft/TypeScript/pull/4598.diff","patch_url":"https://github.com/Microsoft/TypeScript/pull/4598.patch","issue_url":"https://api.github.com/repos/Microsoft/TypeScript/issues/4598","number":4598,"state":"open","locked":false,"title":"Improved checking of destructuring with literal initializers","user":{"login":"ahejlsberg","id":4226954,"avatar_url":"https://avatars.githubusercontent.com/u/4226954?v=3","gravatar_id":"","url":"https://api.github.com/users/ahejlsberg","html_url":"https://github.com/ahejlsberg","followers_url":"https://api.github.com/users/ahejlsberg/followers","following_url":"https://api.github.com/users/ahejlsberg/following{/other_user}","gists_url":"https://api.github.com/users/ahejlsberg/gists{/gist_id}","starred_url":"https://api.github.com/users/ahejlsberg/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/ahejlsberg/subscriptions","organizations_url":"https://api.github.com/users/ahejlsberg/orgs","repos_url":"https://api.github.com/users/ahejlsberg/repos","events_url":"https://api.github.com/users/ahejlsberg/events{/privacy}","received_events_url":"https://api.github.com/users/ahejlsberg/received_events","type":"User","site_admin":false},"body":"This PR makes the checking of destructuring patterns with an object literal or array literal initializers more flexible:\r\n\r\n* When an object literal is contextually typed by the implied type of an object binding pattern, initialized properties in the binding pattern become optional in the object literal, and missing initialized properties from the binding pattern are automatically added as optional properties in the object literal.\r\n* When an array literal is contextually typed by the implied type of an array binding pattern, if the array literal has fewer elements than the array binding pattern, the extra elements are automatically added to the resulting tuple type.\r\n\r\nSome examples:\r\n\r\n```typescript\r\n// Type of foo is (arg?: { x?: number, y?: number }) => void\r\nfunction foo({ x = 0, y = 0 } = {}) { }\r\nfoo();\r\nfoo({});\r\nfoo({ x: 1 });\r\nfoo({ y: 1 });\r\nfoo({ x: 1, y: 1 });\r\n\r\n// Type of bar is (arg?: [number, number]) => void\r\nfunction bar([x = 0, y = 0] = []) { }\r\nbar();\r\nbar([1, 1]);\r\n```\r\n\r\nFixes 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