Correctly combine hash codes for repeated enums. (#556)
Correctly combine hash codes for repeated enums. (#556)

The existing logic in `hashField` is overriding the previously computed
hash codes, which could include values from other fields within the
message. Any message with a repeated enum field with a (relatively) high
tag number will generate a poor hash code which doesn't reflect other
fields.

Co-authored-by: Loren Van Spronsen <84709c0807b4e2f6c888c444b808ad0fe2ec0417@google.com>
dart-lang/protobuf,dart-lang/protobuf,google/protobuf.dart,dart-lang/dart-protobuf,dart-lang/dart-protobuf,google/protobuf.dart,dart-lang/protobuf,google/protobuf.dart,dart-lang/dart-protobuf