Say I have some types:

type A = ...;
type B = ...;
type C = ...;
type MyTypes = A | B | C;

And then I have a generic type transformer:

type Transformed<T extends MyTypes> = ...;

Then I would like to automatically export all transformed types, i.e. autogenerate:

type ATrans = Transformed<A>;
type BTrans = Transformed<B>;
type CTrans = Transformed<C>;

Without having to type that every time I add a new type to MyTypes.

Is this possible?

Thanks,

CodePudding user response：

You can use distributive conditional types:

type A = { tag: 'a' };
type B = { tag: 'B' };
type C = { tag: 'C' };

type MyTypes = A | B | C;

type Transformation<T> = { transformed: T }

type Transformed<T extends MyTypes> = T extends any ? Transformation<T> : never

// Transformation<A> | Transformation<B> | Transformation<C>
type Result = Transformed<MyTypes>

Playground

After this line T extends any union gets distributed