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on this file was d24f17c, checked in by Aleksandar Panovski <apano77@…>, 15 months ago |
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[d24f17c] | 1 | import { Try } from '../Any/Try';
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| 2 | import { Narrowable } from './_Internal';
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| 3 | /**
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| 4 | * @hidden
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| 5 | */
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| 6 | declare type NarrowRaw<A> = (A extends [] ? [] : never) | (A extends Narrowable ? A : never) | ({
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| 7 | [K in keyof A]: A[K] extends Function ? A[K] : NarrowRaw<A[K]>;
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| 8 | });
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| 9 | /**
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| 10 | * Prevent type widening on generic function parameters
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| 11 | * @param A to narrow
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| 12 | * @returns `A`
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| 13 | * @example
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| 14 | * ```ts
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| 15 | * import {F} from 'ts-toolbelt'
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| 16 | *
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| 17 | * declare function foo<A extends any[]>(x: F.Narrow<A>): A;
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| 18 | * declare function bar<A extends object>(x: F.Narrow<A>): A;
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| 19 | *
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| 20 | * const test0 = foo(['e', 2, true, {f: ['g', ['h']]}])
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| 21 | * // `A` inferred : ['e', 2, true, {f: ['g']}]
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| 22 | *
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| 23 | * const test1 = bar({a: 1, b: 'c', d: ['e', 2, true, {f: ['g']}]})
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| 24 | * // `A` inferred : {a: 1, b: 'c', d: ['e', 2, true, {f: ['g']}]}
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| 25 | * ```
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| 26 | */
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| 27 | declare type Narrow<A extends any> = Try<A, [], NarrowRaw<A>>;
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| 28 | export { Narrow };
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