An associated type whose name does not match any of the associated types in the trait was used when implementing the trait.
Erroneous code example:
trait Foo {}
impl Foo for i32 {
type Bar = bool;
}Trait implementations can only implement associated types that are members of the trait in question.
The solution to this problem is to remove the extraneous associated type:
trait Foo {}
impl Foo for i32 {}