combine-type-helper.ts

export type Combine<T> = {
  [K in keyof T]: T[K];
} & {};

type One = {
  one: number;
};
type Two = {
  two: number;
};

type Three = {
  three: number;
};

/*
Shows definition as

type Added = One & Two & Three
*/
type Added = One & Two & Three;

/* Gives good types of:
type Combined = {
    one: number;
    two: number;
    three: number;
}
*/
type Combined1 = Combine<Added>;
type Combined2 = Combine<One & Two & Three>;