Cannot re-export a type when using the --isolatedModules with TS 3.2.2

Question

I probably need to rethink the way we structure our React components. We are using the latest react-scripts that allow Typescript to be used and by default, the isolat

Answer 1

TS 3.8+

You can use type-only imports and exports with --isolatedModules:

// types.ts
export type MyType = { a: string; b: number; };

// main.ts 

// named import/export
import type { MyType } from './types'
export type { MyType }

// re-export
export type { MyType } from './types'

// namespace import
import type * as MyTypes from "./types";
export type RenamedType = MyTypes.MyType;
export { MyTypes };

//     ^ Note the "type" keyword in statements above

Example Playground; Take a look at the PR for possible extension forms and proposals.

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TS 3.7 or older

In previous versions, the following is not possible:

import { MyType } from './types'; 
export { MyType }; // error: Cannot re-export a type with --isolatedModules

export { MyType } from "./types"; // error, like above

Type re-exports have to use a workaround:

import { MyType as MyType_ } from "./types";
export type MyType = MyType_;

// or
export * from "./types"

Answer 2

I am using the same structure personally and stumbled into the same issue after moving to a create-react-app boilerplate which enforces isolatedModules. A workaround that seems to be working in stark contrast to the idea behind isolatedModules is to use export * from "./Component"; in index.ts.