fix HideElementCombinatorImpl toString error
fix HideElementCombinatorImpl toString error

Closes https://github.com/dart-lang/sdk/pull/49984

GitOrigin-RevId: 96ec38ee2c93be22039d09f23f986e5904db4d08
Change-Id: I340083b0d5b32ecc78790dbe9feeefe684672a24
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/259681
Commit-Queue: Brian Wilkerson <1f7641b6b14c52b9163524ab8d9aabff80176f21@google.com>
Reviewed-by: Brian Wilkerson <1f7641b6b14c52b9163524ab8d9aabff80176f21@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk