Update scan.ts

[domoritz]

Otherwise this breaks

$brush.pipe(
    scan(
      (acc, curr) => acc.set(curr.dimension, curr.brush),
      new Map<D, Interval<number>>()
    )
  );

[cartant]

Thanks for opening the PR.

Having a another look at the typings for scan and reduce is on my list of things to do. There are a number of open issues that related to the scan typings: #3150 and #3879. Any changes to the scan typings should take those into account.

The change in this PR appears to be the same as the change suggested in #2897 - which was not merged. See the conversation in that PR for the reasons. I'm not saying that those reasons still apply - and I've not re-read the conversation recently - but it does provide some context.

IMO, now that the testing infrastructure supports dtslint, I don't think we should change the typings until we have dtslint-based tests that document/describe the current behaviour.

Also any changes to the scan typings will likely need to be made to the reduce typings, too.

[domoritz]

Thanks for getting back to me so quickly. I'm going to close this PR then.

I just started using rxjs yesterday and tripped over this issue. I'll just set the types manually for now.

[cartant]

Well, hopefully, I've not discouraged you from contributing, as that wasn't my intention.

Anyway, I'll bump the priority of my writing some dtslint tests for scan and reduce, so that any changes we make to the typings need not be so scary.

[domoritz]

Oh no, I'm not discouraged not at all. I know how open source development goes and I'm impressed how quickly you responded. Thanks for taking my request seriously!