it has below sentences in the Borrow trait docs,
Beyond these generic wrappers that can be used with any type, some types provide optional facets providing potentially costly functionality. An example for such a type is
String
which adds the ability to extend a string to the basicstr
.
I do not understand why this is put in the context of Borrow
trait. What costly functionality
for String
example? What use cases to avoid the costly functionality?