Rust errors / Attributes, macros and features
Rust compiler error · checked with rustc 1.99.0
Rust error E0774: `derive` may only be applied to `struct`s, `enum`s and `union`s
What it meansderive was applied on something which is not a struct, a union or an enum.
What rustc prints
error[E0774]: `derive` may only be applied to `struct`s, `enum`s and `union`s
--> main.rs:2:5
|
2 | #[derive(Clone)] // error!
| ^^^^^^^^^^^^^^^^ not applicable here
3 | type Bar;
| --------- not a `struct`, `enum` or `union`Real output of rustc 1.99.0 compiling the official example below (2021 edition). Your names and line numbers will differ; the first line is the part to match.
E0774Attributes, macros and features
Activein rustc 1.99.0
5related errors linked below
The compiler team's explanation
derive was applied on something which is not a struct, a union or an enum.
Erroneous code example:
trait Foo {
#[derive(Clone)] // error!
type Bar;
}As said above, the derive attribute is only allowed on structs, unions or enums:
#[derive(Clone)] // ok!
struct Bar {
field: u32,
}You can find more information about derive in the Rust Book.
From rustc --explain E0774 (1.99.0), part of the Rust project, MIT or Apache-2.0. Official page.
Related errors
- E0658is unstable
- E0732`#[repr(inttype)]` must be specified for enums with explicit discriminants and non-unit variants
- E0736attribute incompatible with `#[unsafe(naked)]`
- E0795`Some` is an enum variant; expected field at end of `offset_of`
- E0802`CoercePointee` can only be derived on `struct`s with `#[repr(transparent)]`
Up next
Often hit nextE0658: is unstableA related error from the same family.Read it next →Did this answer your question?