Create destructured typescript type one level down

Question

I'd like to destructure type one level down:

type Full = {
  firstLevel: {
    secondLevel: {
      value: string
    }
  }
}

type Desired = {
  secondLevel: {
    value: string
  }
}

I've tried with

type Deconstruct<T,K extends keyof T> = {
  [P in T[K]]: T[K][P];
}

but it doesn't compile. Any ideas without extracting one level down type as separate?

Answer 1

Here are some different ways to achieve what you want: playground

type Full = {
  firstLevel: {
    secondLevel: {
      value: string;
    };
  };
};

// Manual
type DesiredA = Full['firstLevel'];

// Generic deconstruct type
type Deconstruct<T, K extends keyof T = keyof T> = T[K];

// Deconstruct every key
type DesiredB = Deconstruct<Full>;

// Deconstruct only one specific key
type DesiredC = Deconstruct<Full, 'firstLevel'>;

Answer 2

I've already created a solution (oh, it's the most complicated one from all answers:D)

type StripOneLevel<T, K extends keyof T> = {
    [P in keyof T[K]]: T[K][P];
}