[Strict Contract] How to create a binding interface #typescript #tip

index.ts

type Strict<Contract, Class> = Class extends Contract
  ? { [K in keyof Class]: K extends keyof Contract ? Contract[K] : never }
  : Contract;

interface MyContract {
  foo: number;
  bar: boolean;
}

type MyStrictContract = Strict<MyContract, MyClass>;

class MyClass implements MyStrictContract {
  private _qux = '';

  foo = 0;
  bar = false;

  baz() {} // error
}