You tried to use something which is not a trait in a trait position, such as
a bound or `impl`.
Erroneous code example:
```compile_fail,E0404
struct Foo;
struct Bar;
impl Foo for Bar {} // error: `Foo` is not a trait
```
Another erroneous code example:
```compile_fail,E0404
struct Foo;
fn bar<T: Foo>(t: T) {} // error: `Foo` is not a trait
```
Please verify that you didn't misspell the trait's name or otherwise use the
wrong identifier. Example:
```
trait Foo {
// some functions
}
struct Bar;
impl Foo for Bar { // ok!
// functions implementation
}
```
or
```
trait Foo {
// some functions
}
fn bar<T: Foo>(t: T) {} // ok!
```