A spread element in a collection literal, e.g., `[...e]` or `{...?e}`,
can have an `e` of type `Null` or a subtype thereof. This CL adds a test
where this situation is created for different types (`Null`, `Never`,
`X extends Null`) with different collection literals, and with and
without elements of other types. In general, the spread does not
contribute any elements, and hence the element/key/value type is `Never`
such that it has no effect on the element/key/value type of the
collection.
Cf. https://github.com/dart-lang/language/pull/1079.
Change-Id: Ib760bcba18045b1afaa50f65c0e7d0a7fe9a8ab6
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/154693
Commit-Queue: Erik Ernst <eernst@google.com>
Reviewed-by: Nate Bosch <nbosch@google.com>
Johnni Winther