This pull request aims for improved readability, based on issue #146600.
```dart
// before
Set<Color> _distinctVisibleColors() {
final Set<Color> distinctVisibleColors = <Color>{};
if (top.style != BorderStyle.none) {
distinctVisibleColors.add(top.color);
}
if (right.style != BorderStyle.none) {
distinctVisibleColors.add(right.color);
}
if (bottom.style != BorderStyle.none) {
distinctVisibleColors.add(bottom.color);
}
if (left.style != BorderStyle.none) {
distinctVisibleColors.add(left.color);
}
return distinctVisibleColors;
}
// after
Set<Color> _distinctVisibleColors() {
return <Color>{
if (top.style != BorderStyle.none) top.color,
if (right.style != BorderStyle.none) right.color,
if (bottom.style != BorderStyle.none) bottom.color,
if (left.style != BorderStyle.none) left.color,
};
}
```
Most of the repo should be covered in this PR (aside from `flutter_tools/`, since there was a lot going on in there).
