Error code E0719

An associated type value was specified more than once.

Erroneous code example:

#![allow(unused)] fn main() { 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:

#![allow(unused)] fn main() { 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.