bb3467b8e1
* Handle type guard predicates on `Array<T>.find` If the `predicate` function passed to `Array<T>.find` or `ReadonlyArray<T>.find` is a type guard narrowing `value` to type `S`, then any returned element should also be narrowed to `S`. Adding test case and associated baselines * trailing whitespace after merge conflict
13 lines
586 B
TypeScript
13 lines
586 B
TypeScript
// @lib: es2015
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// test fix for #18112, type guard predicates should narrow returned element
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function isNumber(x: any): x is number {
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return typeof x === "number";
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}
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const arrayOfStringsNumbersAndBooleans = ["string", false, 0, "strung", 1, true];
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const foundNumber: number | undefined = arrayOfStringsNumbersAndBooleans.find(isNumber);
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const readonlyArrayOfStringsNumbersAndBooleans = arrayOfStringsNumbersAndBooleans as ReadonlyArray<string | number | boolean>;
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const readonlyFoundNumber: number | undefined = readonlyArrayOfStringsNumbersAndBooleans.find(isNumber);
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