Optionally resolved external types

[saschanaz]

let stream: MSStream;
const inputStream = stream.msDetachStream(); // any in lib.d.ts

// const inputStream = stream.msDetachStream() as Windows.Storage.Streams.IInputStream; from winrt.d.ts

Can we have a potential-any type information that resolves only when we have correct d.ts file? Some small type definitions in DefinitelyTyped refers much bigger ones e.g. node.d.ts that is not always required. (Imagine a library that supports standard types and Node.js types together.) I hope I can just include a small file without node.d.ts or any other unneeded large files.

Maybe somewhat related to old #1402.

[RyanCavanaugh]

If people are using just a very small portion of another library, would they be better served by using structural typing to stub out the useful portion of the consumed type? Just thinking out loud.

[saschanaz]

@RyanCavanaugh I'm not sure I understand. Can you give me an example?

[RyanCavanaugh]

Like instead of

function fn(): SomeOtherLibrary.Point;

you could write

function fn(): { x: number; y: number; }

Assuming that the type is small enough to do this reasonably, of course.

[saschanaz]

That will be great, but the type of IInputStream in my example has a reference to Buffer, Buffer has one to MemoryBuffer, MemoryBuffer has one to IMemoryBufferReference, etc... Maybe one will not need all of them but maybe others will.

[RyanCavanaugh]

Tracking at #31894 now