This lets you test that a callback returns a Future that completes to
a given error. Like Expect.throws(), but async.
At first, I added support for this directly to Expect.throws(), but I
think it's better to minimize the amount of dynamic logic going on in
the language test framework.
I was worried about having to duplicate all of the Expect.throws___()
convenience functions but now that we have generic methods, those
functions aren't that much more convenient.
Change-Id: I8b288945611fa16f8d27056f3cf79181fc22d256
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/97881
Reviewed-by: William Hesse <whesse@google.com>
Bob Nystrom
ffee99d79b