Gotta say, after hearing that rust is not an OOP/Class-inheritance language, and is strongly and explicitly typed, the Deref trait feels like a helluva drug!

Obviously it's not the same thing, but working this out definitely had me making a couple of double takes.

Somewhat awkwardly, I worked it out through the standard lib docs before reading ch 15 of the book (it's more fun this way!).

And for those who want a quick answer:

• Read the Deref docs, especially the deref coercion part
• This allows a variable of a particular type to be implicitly substituted with another variable of a different type.
• It happens any time a reference is passed in/out of a function, including self in method calls.
  • And obviously requires that Deref be implemented.
• So sort() isn't implemented on Vec, it's implemented on the slice type ([T]).
• But Vec implements Deref, substituting [T] for Vec<T> in all function/method calls.
• Which means Vec gets all of the methods implemented on [T] ... almost like Vec is a subclass of [T]!
• And yea, OOP people want to abuse this (see, eg, rust-unofficial on anti-patterns)