Narrow property access of undeclared properties from string index signatures - #19838
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Nathan Shively-Sanders (sandersn) merged 3 commits intoNov 8, 2017
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Previously these accesses did not use control flow to narrow property accesses of undefined properties that are resolved from a string index signature. Now the use control flow to narrow these just like normal properties.
Nathan Shively-Sanders (sandersn)
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Mohamed Hegazy (mhegazy) and
Wesley Wigham (weswigham)
November 8, 2017 17:54
Wesley Wigham (weswigham)
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Wesley Wigham (weswigham)
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Looks good, otherwise.
| type A = { [index: string]: number | null }; | ||
| declare const value: A; | ||
| if (value.foo !== null) { | ||
| value.foo.toExponential() |
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Could you add a value.bar inside the if statement, too? Just to verify that other properties aren't narrowed despite being the same index signature. (I don't think it'll be wrong, I just want to see it in the test)
Wesley Wigham (weswigham)
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Nov 8, 2017
Nathan Shively-Sanders (sandersn)
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narrow-index-signature-property-access
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November 8, 2017 20:10
|
Should this be fixed? interface Dictionary<T> {[K:string] : T|undefined}
const d:Dictionary<any[]> = {};
if (d['k']) d['k'].push(42); // Object is possibly 'undefined'It works with the dot operator — surely d.k and d['k'] are semantically equivalent. |
Contributor
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Yudhi Seymour (@yseymour) that is tracked by #10530 |
ghost
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Previously these accesses did not use control flow to narrow property accesses of undefined properties that are resolved from a string index signature. Now the use control flow to narrow these just like normal properties.
Fixes #17567