bbe6bb9823
Fixes https://github.com/dart-lang/sdk/issues/27468 In addition convert both ILLEGAL_ASYNC_GENERATOR_RETURN_TYPE and ILLEGAL_SYNC_GENERATOR_RETURN_TYPE to CompileTimeErrorCodes. Change-Id: I5f09f3d77dad52b4ba524c86b3e07ac5fac905fd Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/154824 Reviewed-by: Brian Wilkerson <brianwilkerson@google.com> Reviewed-by: Konstantin Shcheglov <scheglov@google.com> Commit-Queue: Samuel Rawlins <srawlins@google.com>