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Head

Extracts the head of a tuple. If you declare Head<[A, B, C]> you will get back A.

type Head<X extends readonly any[]> = ((...args: X) => any) extends (arg: infer U, ...rest: any[]) => any ? U : never;

§Type Parameters

X extends readonly any[]

((...args: X) => any) extends (arg: infer U, ...rest: any[]) => any ? U : never