0764c70cd9
Pre-nnbd, add and toggle were allowed to return null, but with the change in the Set interface, they must return a non-nullable bool. Change-Id: I1dfcb43d8c816f46f847d22d6f62507c6a77e4a4 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/141500 Commit-Queue: Srujan Gaddam <srujzs@google.com> Reviewed-by: Stephen Adams <sra@google.com>