Things on this page are fragmentary and immature notes/thoughts of the author. Please read with your own judgement!

1. In short, do NOT implement the Deref trait unless you are absolutely sure that it's needed! According to Rust Official Doc - Deref, Deref should only be implemented for smart pointers. The Rust Programing Language book has a chapter covering smart pointers , however, the definition is vague. In the context of implementing Deref for smart pointers, smart pointers are types that act like pointers but are not supposed to have methods on their own (so ambiguity during method resolution are avoid). For example, Box implements Deref so that you can conveniently use methods of the target type. But if you look at the documentation of Box, the things you can do with the Box itself, like Box::leak, are non-method functions. This means that you always have to qualify them, like Box::leak(my_box).

2. If you do implement Deref<Target = U> on a type T, and it proved necessary to implement a generic trait Trait<S> on T. Then one should ensure that the implementations of Trait<S> for different parameters S are not scattered across T and U. Put simply, either T or U should host all existing Trait<S> implementations. Note that the preceding "or" is inclusive, meaning that both T and U can host some Trait<S> implementations, as long as they both host all of them.

References

• Rust Official Doc - Deref

• Deref Confusion

• Is Deref bad for caching?

• Mistakes with Rust smart pointers: when Deref goes wrong (fuzzypixelz.com)

• Rust Issue - Deref documentation: Remove references to "smart pointers"