Don’t allow an object literal with a spread as a fallback for destructuring a property not present in all constituents#43783
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andrewbranch merged 2 commits intomicrosoft:masterfrom Apr 23, 2021
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…turing a property not present in all constituents
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@typescript-bot user test this |
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Heya @andrewbranch, I've started to run the parallelized community code test suite on this PR at 2950db9. You can monitor the build here. |
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Heya @andrewbranch, I've started to run the extended test suite on this PR at 2950db9. You can monitor the build here. |
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The user suite test run you requested has finished and failed. I've opened a PR with the baseline diff from master. |
sandersn
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RyanCavanaugh
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Fixes #43174
#31711 allowed object literals as fallbacks for destructuring, such that
const { x } = foo || {}was allowed even though{}has no propertyx. The only criteria for an object constituent of a union to be considered to have{ [key: string]: undefined }index signature was that it be an object literal—the common pattern seems to be an empty object literal, but any object literal ought to avoid excess property pitfalls through aliasing.... except, that logic neglected spreads, which could introduce arbitrary extra properties of arbitrary types, as demonstrated in #43174.