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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Optional chaining with non null operator is unsafe, because it could throw an exception","articleBody":"**TypeScript Version:**  3.7.2\r\n\r\n**Search Terms:** optional chaining, non null operator\r\n\r\n**Code**\r\n\r\nThis input\r\n\r\n```ts\r\na?.b!.c\r\n```\r\n\r\nwill compile to\r\n\r\n```js\r\n((_a = a) === null || _a === void 0 ? void 0 : _a.b).c;\r\n```\r\n\r\nBut it's unsafe, because if `a` is `null` or `undefined`, will throw an exception:\r\n\r\n```js\r\n   ((_a = a) === null || _a === void 0 ? void 0 : _a.b).c\r\n=\u003e ((_a = null) === null || _a === void 0 ? void 0 : _a.b).c\r\n=\u003e (null === null || _a === void 0 ? void 0 : _a.b).c\r\n=\u003e (true ? void 0 : _a.b).c\r\n=\u003e undefined.c\r\n```\r\n\r\nIMO we should not raise this exception.\r\n\r\n**Expected behavior:**\r\n\r\nWould be better to compile to\r\n\r\n```js\r\n(_a = a) === null || _a === void 0 ? void 0 : _a.b.c;\r\n```\r\n\r\nSo `a` could be null or undefined and it'll not raise an exception anymore.\r\n\r\n**Playground Link:** [Playground](http://www.typescriptlang.org/play/#code/DYUwLgBAhgXNB2BPAUFA-AOgEYEIMGMg)\r\n\r\n**Related Issues:** There was a lot of discussion here, but was more focused in the type system, not about the code output that raise wrongly an exception.\r\n- https://github.com/microsoft/TypeScript/issues/34875\r\n- https://github.com/microsoft/TypeScript/issues/35025\r\n- https://github.com/microsoft/TypeScript/issues/35071\r\n\r\nAlso this bug was reported in Babel and already there is a PR to fix that in Babel:\r\n- issue: https://github.com/babel/babel/issues/10959\r\n- pr: https://github.com/babel/babel/pull/10961\r\n\r\n**In this issue I'm saying only about the output, not about the type system.**","author":{"url":"https://github.com/macabeus","@type":"Person","name":"macabeus"},"datePublished":"2020-01-06T18:07:13.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":23},"url":"https://github.com/36031/TypeScript/issues/36031"}