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/** Type alias for something that may or may not be wrapped in a promise. */
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export type Awaitable<T> = T | Promise<T>
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/** Type alias for something that may be undefined. */
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export type Maybe<T> = T | undefined
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export type Either<T1, T2> = Left<T1> | Right<T2>
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export type Left<T> = [T, undefined]
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export type Right<T> = [undefined, T]
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export function isLeft<T1, T2>(what: Either<T1, T2>): what is Left<T1> {
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return typeof what[1] === 'undefined'
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}
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export function isRight<T1, T2>(what: Either<T1, T2>): what is Right<T2> {
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return typeof what[0] === 'undefined'
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}
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export function left<T>(what: T): Left<T> {
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return [what, undefined]
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}
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export function right<T>(what: T): Right<T> {
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return [undefined, what]
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}
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/** Type alias for a callback that accepts a typed argument. */
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export type ParameterizedCallback<T> = ((arg: T) => any)
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/** A key-value form of a given type. */
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export type KeyValue<T> = {key: string, value: T}
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/** Simple helper method to verify that a key is a keyof some object. */
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export function isKeyof<T>(key: unknown, obj: T): key is keyof T {
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if ( typeof key !== 'string' && typeof key !== 'symbol' ) {
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return false
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}
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return key in obj
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}
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/** A typescript-compatible version of Object.hasOwnProperty. */
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export function hasOwnProperty<X extends {}, Y extends PropertyKey>(obj: X, prop: Y): obj is X & Record<Y, unknown> { // eslint-disable-line @typescript-eslint/ban-types
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return Object.hasOwnProperty.call(obj, prop)
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}
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/**
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* TypeScript helper for creating tagged-types.
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*/
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export interface TypeTag<S extends string> {
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readonly __typeTag: S
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}
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export type PrefixTypeArray<T, TArr extends unknown[]> = [T, ...TArr]
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export type SuffixTypeArray<TArr extends unknown[], T> = [...TArr, T]
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export type TypeArraySignature<TArr extends unknown[], TReturn> = (...params: TArr) => TReturn
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