An associated type value was specified more than once.
Erroneous code example:
#![feature(associated_type_bounds)]
trait FooTrait {}
trait BarTrait {}
// error: associated type `Item` in trait `Iterator` is specified twice
struct Foo<T: Iterator<Item: FooTrait, Item: BarTrait>> { f: T }Item in trait Iterator cannot be specified multiple times for struct Foo.
To fix this, create a new trait that is a combination of the desired traits and
specify the associated type with the new trait.
Corrected example:
#![feature(associated_type_bounds)]
trait FooTrait {}
trait BarTrait {}
trait FooBarTrait: FooTrait + BarTrait {}
struct Foo<T: Iterator<Item: FooBarTrait>> { f: T } // ok!For more information about associated types, see the book. For more information on associated type bounds, see RFC 2289.