Traits

Trait
- A trait defines the functionality a particular type has and can share with other types¹
- Limitations
  - You can’t implement external traits on external types.
  - A trait can be implemented on a type only if either the trait or the type, or both, are local to our crate
Traits in Rust are interfaces (shared behavior). However, unlike in other languages (like Golang) default implementations can be defined.
- Can use generic type parameters to reduce duplication (DRY) but also enforce behavior.
Traits can be conditionally implemented for any type that implements another trait.
Blanket Implementations
- Implementations of a trait on any type that satisfies the trait bounds
- Used extensively in the Rust standard library
- Done by using a trait bound with an impl block that uses generics

The ability to specify a return type only by the trait it implements is especially useful in the context of closures and iterators.

Downsides of too many trait bounds
- Each generic has its own trait bounds, so functions with multiple generic type parameters can contain lots of trait bound information between the function’s name and its parameter list.
  - Can be remedied with a where clause
- We can also specify more than one trait bound.
The impl Trait syntax is actually syntactic sugar for a trait bound.
Instead of a concrete type for the item parameter, we specify the impl keyword and the trait name

Footnotes