For some types it makes sense to distinguish between nullability as a
property of including null and the declared nullability, such as for
type-parameter types and FutureOr types. This CL introduces the
separation between the two concepts. The plan is to use that when
implementing FutureOrType.
Bug: https://github.com/dart-lang/sdk/issues/40123
Change-Id: I90b45bea768e89c213d021d360a481d38377c682
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/147903
Reviewed-by: Johnni Winther <johnniwinther@google.com>
Commit-Queue: Dmitry Stefantsov <dmitryas@google.com>
Dmitry Stefantsov
e53e5f2475