Something other than a type or an associated type was given.
Erroneous code example:
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!