A type that is not a trait was used in a trait position, such as a bound
or impl
.
Erroneous code example:
struct Foo;
struct Bar;
impl Foo for Bar {} // error: `Foo` is not a trait
fn baz<T: Foo>(t: T) {} // error: `Foo` is not a trait
RunAnother erroneous code example:
type Foo = Iterator<Item=String>;
fn bar<T: Foo>(t: T) {} // error: `Foo` is a type alias
RunPlease verify that the trait’s name was not misspelled or that the right identifier was used. Example:
trait Foo {
// some functions
}
struct Bar;
impl Foo for Bar { // ok!
// functions implementation
}
fn baz<T: Foo>(t: T) {} // ok!
RunAlternatively, you could introduce a new trait with your desired restrictions as a super trait:
trait Qux: Foo {} // Anything that implements Qux also needs to implement Foo
fn baz<T: Qux>(t: T) {} // also ok!
RunFinally, if you are on nightly and want to use a trait alias
instead of a type alias, you should use #![feature(trait_alias)]
:
#![feature(trait_alias)]
trait Foo = Iterator<Item=String>;
fn bar<T: Foo>(t: T) {} // ok!
Run