a58052974e
This CL makes several adjustments to the spec_parser grammar Dart.g, such that the spec_parser can parse the proposed NNBD constructs, cf. language PR #293. Change-Id: Ieec00259d73b6037d6a87d5c97cfac40186baef0 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/101500 Reviewed-by: Leaf Petersen <leafp@google.com> Commit-Queue: Erik Ernst <eernst@google.com>