TypeScript: Cannot 'export default' abstract, ambient class or interface

We should just allow these. It’s a strange inconsistency, the workaround is more verbose, and the error gives you no help getting to the workaround.

Unsupported export default patterns:

• export default abstract class C { } Added by #14657
• export default declare class C { }
• export default interface I { } Added by #16040
• export default enum E { }
• export default const enum E { }
• export default namespace N { }
• export default type T = { }

These two are by desing. We have felt that the export default syntax is already long enough, so no modifiers are needed. for a workaround use:

declare class  C {}
export default C;

should also cover interfaces (https://github.com/Microsoft/TypeScript/issues/3914):

export default interface User {
    wpUserID: string;
}

I would prefer support for export default enum and export default const enum too. (#3320)

@mhegazy what about export default type foo = {} ?

And namespaces: export default namespace foo { ... } (#7407)

Found this when trying export default enum. Is this really not implemented yet? (6 years)

Does this mean a namespace can be anonymous?

export default namespace {
    export var foo = 100;
}

What about an interface?

export default interface {
    foo: number;
}

Really look forward to #18628! Thanks @NaridaL. 👏👏 👏

@mhegazy for full symmetry with JS export forms, consider (strawman syntax) export default as ...:

not sure what that means…

export default as number

but if it is a .d.ts, we chose not to have a special syntax for this, and the recommendation here is to use

declare cosnt _t: number;
export default _t;

I’m OK with leaving it as is if the reasoning is that interfaces, et al, are not vaid EcmaScript and #3917 is implemented.