| The rule for packages in this directory is that they can depend on |
| nothing but core Dart packages. They can't depend on `dart:ui`, they |
| can't depend on any `package:`, and they can't depend on anything |
| outside this directory. |
| |
| Currently they do depend on dart:ui, but only for `VoidCallback` and |
| `hashValues` (and maybe one day `hashList` and `lerpDouble`), which |
| are all intended to be moved out of `dart:ui` and into `dart:core`. |
| |
| See also: |
| |
| * https://github.com/dart-lang/sdk/issues/27791 (`VoidCallback`) |
| * https://github.com/dart-lang/sdk/issues/25217 (`hashValues`, `hashList`, and `lerpDouble`) |
