lib/common-utils.ts

// Copyright (c) 2022, Compiler Explorer Authors
// All rights reserved.
//
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// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
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export function isString(x: any): x is string {
    return typeof x === 'string' || x instanceof String;
}

// Object.keys is typed as returning :string[] for some reason
// This util is for cases where the key is a union of a few possible keys and we
// want the resulting array properly typed.
export function keys<K extends string | number | symbol>(o: Partial<Record<K, any>>): K[] {
    return Object.keys(o) as K[];
}

export function unique<V>(arr: V[]): V[] {
    return [...new Set(arr)];
}

export function intersection<V>(a: V[], b: V[]): V[] {
    const B = new Set(b);
    return [...a].filter(item => B.has(item));
}

// arr.filter(x => x !== null) returns a (T | null)[] even though it is a T[]
// Apparently the idiomatic solution is arr.filter((x): x is T => x !== null), but this is shorter (and the type
// predicate also isn't type checked so it doesn't seem safe to me)
export function remove<U, V extends U>(arr: U[], v: V) {
    return arr.filter(item => item !== v) as Exclude<U, V extends null | undefined ? V : never>[];
}
// https://www.typescriptlang.org/play?#code/KYDwDg9gTgLgBAMwK4DsDGMCWEVysAWwgDdgAeAVQBo4A1OUGYFAEwGc4KA+ACgEMoUAFycA2gF0axEbQCUcAN4AoOKrzAYSKLgFQAdAkwAbJlB6YmBOAF4ucC4TgBCa9bjF5fDgFEQaI0gs5NR0DCBMrBwoSEZGcAA+cKhBhijALHAA-KEiaaRQXBIA3EoAvkpKQf4CwHBoOGzwuiI8jVCYKADmCXDRsbLFFfUojXAgNupEpPyCNH1GsiUA9EtqcAB6mUMN8ACeE-hTwDNQNABECBAQZ4tKK2ubFUA

// For Array.prototype.sort
export function basic_comparator<T>(a: T, b: T) {
    if (a < b) {
        return -1;
    } else if (a > b) {
        return 1;
    } else {
        return 0;
    }
}

// https://stackoverflow.com/questions/41253310/typescript-retrieve-element-type-information-from-array-type
export type ElementType<ArrayType extends readonly unknown[]> = ArrayType extends readonly (infer T)[] ? T : never;