export default type

Search Terms

export default type

Suggestion

Allow export default for type.

Use Cases

It would be very nice to have export default type to match with other default exports such as classes and interfaces.

Right now it looks very inconsistent to be able to export anything as default and only types with named export:

export default class MyClass {}
export default interface MyInterface {}
export type MyType = {}

The only way to achieve this now is to use annoying workaround:

type X = number | string

export { X as default }

This may cause confusion for newbies as there are no clear reasons why classes and interfaces can be exported as default, but not the types.

Examples

// x.ts
export default type X = {}

// main.ts
import X from './x'

Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

(not sure on the last)

この issue には型に default export を追加するための構文例がありますが、ソースファイル、テスト、エントリポイントは示されていません。まず、既存の default class export と interface export の処理を追跡し、次に parser、checker、emit のどの動作をカバレッジの対象にする必要があるかを判断してください。提案された構文が、出力される JavaScript を変更せずに示された import で動作すれば完了です。