1 An associated type value was specified more than once.
3 Erroneous code example:
6 #![feature(associated_type_bounds)]
11 // error: associated type `Item` in trait `Iterator` is specified twice
12 struct Foo<T: Iterator<Item: FooTrait, Item: BarTrait>> { f: T }
15 `Item` in trait `Iterator` cannot be specified multiple times for struct `Foo`.
16 To fix this, create a new trait that is a combination of the desired traits and
17 specify the associated type with the new trait.
22 #![feature(associated_type_bounds)]
26 trait FooBarTrait: FooTrait + BarTrait {}
28 struct Foo<T: Iterator<Item: FooBarTrait>> { f: T } // ok!
31 For more information about associated types, see [the book][bk-at]. For more
32 information on associated type bounds, see [RFC 2289][rfc-2289].
34 [bk-at]: https://doc.rust-lang.org/book/ch19-03-advanced-traits.html#specifying-placeholder-types-in-trait-definitions-with-associated-types
35 [rfc-2289]: https://rust-lang.github.io/rfcs/2289-associated-type-bounds.html