flatten is not inferring type properly

[AlexGalays]

Hello,

Using Typescript 1.8.7,

I have stream.map(fnThatReturnsAStreamOfBooleans). That properly get inferred to Stream<Stream<boolean>>

However, if I finish the chain with flatten(), the final type is Stream<{}> instead of Stream<boolean>

Example:

const stream: Stream<string> = Stream.create({
    start: listener => {},
    stop: () => {}
})

const stream2: Stream<boolean> = Stream.create({
    start: listener => {},
    stop: () => {}
})

const f = stream.map(x => stream2).flatten()

f is a stream<{}>

I suspect the T in flatten completely redefines the T of the Stream.

I think it would be best to remove this whole T extends Stream<R> for now.

PS: this seems to be related: microsoft/TypeScript#1290

Arguably, this shows a single operation flatMap is not such a bad idea after all :p

[staltz]

Thanks for the report

[staltz]

Fixed in 2.1.0