Auto-import fails for default exports that are the result of declaration merging

[dfreeman]

TypeScript Version: 3.0.0-dev.20180531

Search Terms: various combinations of merge, default, import, suggestion, auto

Code

This issue occurs when a default export is augmented in another declaration, which I originally ran into when testing out DefinitelyTyped/DefinitelyTyped#26154

// file: a.ts
declare module 'my-class' {
    export default class MyClass { /* ... */ }
}

// file: b.ts
declare module 'my-class' {
    export default interface MyClass { /* ... */ }
}

Expected behavior:

Typing MyClass and requesting suggested fixes includes the option to auto-import MyClass from 'my-class'.

Actual behavior:

An entry in MyClass appears in the list, but selecting it does nothing. Debugging indicates that this assertion is failing because the exportInfos array is empty.

I have a branch with a new (initially failing) unit test and a fix, but wanted to get a bug filed first.

Playground Link: N/A (as far as I can tell, suggested fixes aren't available in the playground)

Related Issues: I found #14080 in the course of searching around, but parallel export defaults appear to work fine for augmentation at least for the use cases I've run into.

[mhegazy]

This is just not a supported pattern at the moment. you can not augment a default export. #14080 tracks fixing that. i suggests adding this repro to #14080

[dfreeman]

I'm a bit confused — the augmentation itself appears to work exactly as expected, e.g. in this playground. The only problem I was running into was with the auto-import.

Is it possible default export augmentation was incidentally supported as part of some other change and just doesn't have any test coverage?

[mhegazy]

looks like we fixed #14080 at some point..