- Add an underscore to private/internal symbols
- Make access levels explicit, even when they’re implied from context
- Conform to max line length of 80 characters
- Conformances declared on separate extensions that implement them
- Arrange member declarations so that stored properties appear first
- Expand single-letter function and type parameter names where there is an obvious name that’s more descriptive
- RangeReplaceableCollection.fastApplicationEnumeration → CollectionDifference._fastEnumeratedApply
