Would it make sense to introduce a `ShallowClone` trait with `Clone` as a subtrait? `ShallowClone` would be almost like a marker trait and it would provide the method `shallow_clone` which may call `clone` by default. If people see that both `ShallowClone` and `Clone` is implemented for a type, then they can infer that the type is cheaply cloneable

[apoelstra]

          8eeab8f2e6dc61eba299e57b282ecf677a9bce0a: Would it make sense to introduce a `ShallowClone` trait with `Clone` as a subtrait? `ShallowClone` would be almost like a marker trait and it would provide the method `shallow_clone` which may call `clone` by default. If people see that both `ShallowClone` and `Clone` is implemented for a type, then they can infer that the type is cheaply cloneable

Originally posted by @uncomputable in #231 (comment)

[apoelstra]

Yep, I like this idea.