TypeScript 推斷不適用於嵌套 generics，推斷類型為未知

Question

我需要 TypeScript 才能在我的“wrongInference”function 的返回值中正確推斷類型 T。

interface Foo {
  bar: string;
}

const paramFunction = (bar: string): Foo => ({
  bar
});

type GenericFunction<T> = (...args: any) => T;

export const wrongInference = <T, F extends GenericFunction<T>>(
  paramFunction: F
) => ({
  data: {} as T,
});

const wrongType = wrongInference(paramFunction);

TypeScript 將data值推斷為未知。 有沒有辦法解決？

Answer 1

以下是如何使用條件返回類型和infer關鍵字解決問題：

interface Foo {
    bar: string;
}

const paramFunction = (bar: string): Foo => ({
    bar
});

type GenericFunction<T> = (...args: any) => T;

export const wrongInference = <F extends GenericFunction<any>>(
    paramFunction: F
): F extends GenericFunction<infer T> ? { data: T } : never => ({
    data: {},
} as any);

const wrongType = wrongInference(paramFunction);

TypeScript 操場