Replace Union

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题目

Given an union of types and array of type pairs to replace ([[string, number], [Date, null]]), return a new union replaced with the type pairs.

解答

type UnionInType<T, U extends [any, any][]> = U extends [
  infer A extends [any, any],
  ...infer B extends [any, any][]
]
  ? T extends A[0]
    ? A[1]
    : UnionInType<T, B>
  : T;


type UnionReplace<T, U extends [any, any][]> = T extends T
  ? UnionInType<T, U>
  : never;