How to infer type parameters from other type parameters?

I want to implement a sorting function that can take the value of an object using a function, but at the moment I can't infer the return value of the function that takes the value.

type TKey<TData> = ((data: TData) => any)    interface SortingConfig<    TData,    TExtractor extends TKey<TData>,    TValue =      TExtractor extends (data: TData) => infer R ? R : never> {    extractor: TExtractor,    comparator?: (a: TValue, b: TValue) => number  }    function test1<TData, TExtractor extends TKey<TData>>(    value: TData,    conf: SortingConfig<TData, TExtractor>  ) {}    test1({    a: 1,    b: "string"  }, {    // extractor type: (data: {a: number, b: string}) => string    // The type of comparator is wrong, parameter type should be the return type of extractor    extractor: data => data.b,    // comparator type: (a: any, b: any) => any    // expect: (a: string, b: string) => number    comparator: (a, b) => a  })    /**   * This works, but unfortunately I need to write it in the above way   */  function test2<    TData,    TExtractor extends TKey<TData>,    TValue = TExtractor extends (data: TData) => infer R ? R : never  >(    data: TData,     extractor: TExtractor,     comparator: (a: TValue, b: TValue) => number  ) {}    // Put the comparator and extractor outside the conf object and it works  // extractor type: (data: {a: number, b: string}) => number  // comparator type: (a: number, b: number) => number  test2({a: 1, b: "string"}, data => data.a, (a, b) => a)  

https://stackoverflow.com/questions/66077029/how-to-infer-type-parameters-from-other-type-parameters February 06, 2021 at 08:40PM