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R.anyPass() can function as a type guard #695

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Jul 29, 2023
Merged

R.anyPass() can function as a type guard #695

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1 change: 1 addition & 0 deletions files/index.d.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -391,6 +391,7 @@ Notes:

*/
// @SINGLE_MARKER
export function anyPass<T, U extends T[]>(predicates: { [K in keyof U]: (x: T) => x is U[K]; }): (input: T) => input is U[number];
export function anyPass<T>(predicates: ((x: T) => boolean)[]): (input: T) => boolean;
export function anyPass<T>(predicates: ((...inputs: T[]) => boolean)[]): (...inputs: T[]) => boolean;

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15 changes: 15 additions & 0 deletions source/anyPass-spec.ts
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Expand Up @@ -32,4 +32,19 @@ describe('anyPass', () => {
const filtered2 = xs.filter(pred)
filtered2 // $ExpectType number[]
})
it('functions as a type guard', () => {
const isString = (x: unknown): x is string => typeof x === 'string';
const isNumber = (x: unknown): x is number => typeof x === 'number';
const isBoolean = (x: unknown): x is boolean => typeof x === 'boolean';

const isStringNumberOrBoolean = anyPass([isString, isNumber, isBoolean]);

isStringNumberOrBoolean // $ExpectType (input: unknown) => input is string | number | boolean

const aValue: unknown = 1;

if (isStringNumberOrBoolean(aValue)) {
aValue // $ExpectType string | number | boolean
}
})
})