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题目

Implement Format<T extends string> generic.

For example,

type FormatCase1 = Format<"%sabc">; // FormatCase1 : string => string
type FormatCase2 = Format<"%s%dabc">; // FormatCase2 : string => number => string
type FormatCase3 = Format<"sdabc">; // FormatCase3 :  string
type FormatCase4 = Format<"sd%abc">; // FormatCase4 :  string

解答

type MapDict = {
  s: string;
  d: number;
};

type Format<T extends string> = T extends `${string}%${infer M}${infer R}`
  ? M extends keyof MapDict
    ? (x: MapDict[M]) => Format<R>
    : Format<R>
  : string;