What is the process for exporting an interface from a namespace?

How can I export an interface from a namespace in typescript? Is this only possible with declaration files? Let me show you what I'm trying to achieve:

namespace Foo {
  export interface Bar {}
  export class Baz {}
}

export const { Baz } = Foo; // Working as expected
export const { Bar } = Foo; // Error: Type 'typeof Foo' does not have a property 'Bar'

Typescript 3.3.1

It's interesting to note that the official documentation includes this use case, which is why I was puzzled when it didn't work: https://www.typescriptlang.org/docs/handbook/namespaces.html

Update (thanks Titian):

My main goal was to export this type, and I managed to do so by following Titian's advice:

namespace Foo {
    export interface Bar {}
    export class Baz {}
}

export const type Bar = Foo.Bar // now exportable

Answer №1

When you attempt to utilize the interface in a specific location where a value is required, it may cause confusion. Classes serve as both types and values, which explains why everything functions smoothly.

To ensure proper functionality, use the interface within a type annotation:

namespace Example {
    export interface Item {}
    export class Element {}
}

Example.Element // Functions perfectly
let item : Example.Item // works fine

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