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Something other than a type or an associated type was given.
Erroneous code example:
```compile_fail,E0575
enum Rick { Morty }
let _: <u8 as Rick>::Morty; // error!
trait Age {
type Empire;
fn Mythology() {}
}
impl Age for u8 {
type Empire = u16;
}
let _: <u8 as Age>::Mythology; // error!
```
In both cases, we're declaring a variable (called `_`) and we're giving it a
type. However, `<u8 as Rick>::Morty` and `<u8 as Age>::Mythology` aren't types,
therefore the compiler throws an error.
`<u8 as Rick>::Morty` is an enum variant, you cannot use a variant as a type,
you have to use the enum directly:
```
enum Rick { Morty }
let _: Rick; // ok!
```
`<u8 as Age>::Mythology` is a trait method, which is definitely not a type.
However, the `Age` trait provides an associated type `Empire` which can be
used as a type:
```
trait Age {
type Empire;
fn Mythology() {}
}
impl Age for u8 {
type Empire = u16;
}
let _: <u8 as Age>::Empire; // ok!
```
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