We did not previously prevent `class C implements FutureOr<int> ..` and
similar declarations. However, it offers only very little value to
allow this, and possibly creates some complications. This CL makes all
these subtype relationships a compile-time error.
The wording of the constraint on `\WITH{} clause` was also adjusted to
remove some potential interpretations which are unintended (like
preventing `with List<dynamic>`, which should be OK).
Change-Id: I626c2767befa7a3cb3092b0ba5cb463e9456d431
Reviewed-on: https://dart-review.googlesource.com/63583
Reviewed-by: Lasse R.H. Nielsen <lrn@google.com>
Erik Ernst
b803d74c9b