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loucadufault/tuple-equaling-union.ts

Last active May 28, 2025 13:30
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TypeScript pattern for enforcing that a tuple have the exact same items as the members of a union (one-liner, avoids linter errors)
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tuple-equaling-union.ts
import type { IsEqual, TupleToUnion } from 'type-fest'
type IsTupleEqual<TTuple, TExpected> = IsEqual<TupleToUnion<TTuple>, TExpected>
// ---
type ExpectedItem = 'a' | 'b' | 'c'
const myArr = ['b', 'c', 'a'] as const
true satisfies IsTupleEqual<typeof myArr, ExpectedItem> // ts error if myArr has any fewer or excess items
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loucadufault commented May 27, 2025 •
edited
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https://www.typescriptlang.org/play/?#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-YTP4A2bQOAghDgjnQ2oGBpNFptDq9HrdAbQYZQNRRx3OqAAZndJuZpm91lSvsyAcWOXWxXbawjewd+PhOEpqMazRGJYdkwAQiQHK95ktcqsSt24KWjic4GcLlcbu0dOCHkYngMnVOZ7N3g3Pn6nH2UBisRmR8Wxwcy6fXi6523F53QzIHOGOw9q+a6nOclzXLce6CAehhHpO04fhe4TpM2ahAA

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